NSI-189 10 mg ► 100 capsules

Support for hippocampal neurogenesis and improvement of cognitive ability

This protocol is designed for people seeking to support the birth of new neurons in the hippocampus, promote memory formation, and contribute to the maintenance of cognitive function by stimulating neurogenic processes that naturally decline with age and stress.

• Dosage during the adaptation phase (days 1-5): Start with 10 mg (1 capsule) once a day, preferably in the morning with breakfast. This phase allows the body to gradually adapt to the introduction of the compound and establishes individual tolerance without introducing abrupt changes in neuronal signaling. The low initial dose allows for evaluation of individual response and minimizes the possibility of adverse effects related to sudden introduction.

• Maintenance dosage (from day 6): Increase to 20-30 mg daily, divided into two doses. The standard protocol is 10 mg (1 capsule) in the morning with breakfast and 10-20 mg (1-2 capsules) at midday with lunch, for a total of 20-30 mg daily. This dosage provides a sustained supply of the compound during waking hours when neuronal activity and plasticity processes are most active, and approximates doses that have been investigated in human clinical studies.

• Advanced dosage (after 4-8 weeks of continuous use): For individuals seeking to maximize neurogenic effects and who have adequately tolerated maintenance doses, the dose may be gradually increased to 40 mg daily, divided into two 20 mg doses (2 capsules per dose), one in the morning with breakfast and the other at midday with lunch. This higher dosage range should only be implemented after establishing adequate tolerance with lower doses and should be considered for use in the context of specific cognitive optimization goals.

• Frequency of administration : It has been observed that administering NSI-189 with food may enhance absorption and reduce any potential for gastrointestinal discomfort. Morning administration aligns with periods of heightened cognitive activity and may synchronize with natural circadian rhythms of neurogenesis that exhibit diurnal variation. The second dose at midday provides sustained levels throughout the afternoon when consolidation of memories from morning experiences is occurring. Late nighttime administration should be avoided, as some users have reported effects on sleep when NSI-189 is taken close to bedtime, although this response varies among individuals.

• Cycle Duration: The neurogenic effects of NSI-189 are cumulative and progressive, with studies suggesting that structural changes in the hippocampus, such as increased volume, develop over weeks to months of continuous use. This protocol can be followed continuously for 12–16 weeks to allow for the full expression of effects on neurogenesis, dendritic arborization, and synaptic formation. After this initial period, a 2–4 ​​week break can be implemented to allow for assessment of baseline cognitive function without supplementation and to prevent the potential development of tolerance or desensitization of signaling pathways. After the break, the protocol can be resumed, starting with maintenance doses without the need to repeat the entire adaptation phase if previous tolerance was good. Many people opt for repeated cycles of 12–16 weeks of use followed by 2–4 weeks of break for a year or more, as ongoing support for neurogenesis can be beneficial.

• Special considerations: The effectiveness of this protocol for supporting neurogenesis is maximized when combined with lifestyle factors that also promote neurogenesis and brain health, including regular aerobic exercise, which is one of the most potent stimuli of hippocampal neurogenesis by increasing BDNF; cognitive stimulation through learning new skills, reading, and problem-solving; adequate quality sleep of 7–9 hours, which is critical for memory consolidation and neuronal repair processes; a diet rich in omega-3 fatty acids, particularly DHA, which is a structural component of neuronal membranes; and management of chronic stress through stress reduction techniques, since elevated cortisol inhibits neurogenesis. Supplementation with NAD+ precursors such as NMN, which supports mitochondrial energy metabolism, or with cofactors for brain function such as B vitamins, can be complementary to NSI-189.

Promotion of synaptic plasticity and optimization of learning

This protocol is geared towards people who seek to improve their brain's ability to form new synaptic connections, to strengthen existing synapses through long-term potentiation, and to facilitate the acquisition of new skills and knowledge by optimizing plasticity mechanisms.

• Dosage during adaptation phase (days 1-5): Start with 10 mg (1 capsule) once daily in the morning with breakfast. This gradual introduction allows synaptic signaling systems to adjust to the presence of the compound without causing abrupt changes in excitation-inhibition balance that could result in adverse effects.

• Maintenance dosage (from day 6): Increase to 20 mg daily, divided into two 10 mg doses (1 capsule per dose), one in the morning before or with breakfast and the other at midday before or with lunch. This dosage provides sustained modulation of glutamate receptors and neurotrophic signaling during periods of active learning and practice, supporting the induction of long-term potentiation, which is an activity-dependent process.

• Intensive dosage (for periods of demanding learning): During specific periods of intensive learning, such as during the acquisition of a new complex skill, exam preparation, or structured cognitive training, the dosage may be temporarily increased to 30–40 mg daily, divided into two or three doses. The suggested protocol is 10–20 mg (1–2 capsules) in the morning, 10 mg (1 capsule) at midday, and 10 mg (1 capsule) in the mid-afternoon, approximately 4–5 hours before bedtime. This higher dosage should be limited to periods of 4–8 weeks during the intensive learning phase, followed by a return to maintenance dosage.

• Administration frequency: For synaptic plasticity and learning goals, the timing of administration in relation to practice or study periods may be relevant. Some users prefer to take a morning dose 30–60 minutes before learning or practice sessions to ensure that levels of the compound are elevated during the period of new memory encoding. Administration with a small amount of food may promote absorption while minimizing gastrointestinal discomfort. For motor skill learning, administration before physical practice sessions may be optimal. For academic or cognitive learning, distributing doses before major study periods may promote consolidation.

• Cycle duration: This protocol can be followed for the duration of an intensive learning period, typically 8–16 weeks, which corresponds to the typical duration of an academic semester or a complex skill acquisition phase. After the learning period, a maintenance period with a reduced dose of 10–20 mg daily for 4–8 weeks can be implemented to support continued consolidation of acquired memories, followed by a 2–4 ​​week break. The cycle can be repeated when a new intensive learning period is anticipated. For continuous support of synaptic plasticity outside of specific learning periods, the use of a maintenance dose of 20 mg daily in cycles of 12 weeks on, 2–4 weeks off may be appropriate.

• Special considerations: Synaptic plasticity is an activity-dependent process, meaning that NSI-189 provides the molecular substrate for plasticity, but the formation of specific connections requires appropriate neuronal activity through practice, study, or experience. Effectiveness is maximized through distributed practice rather than massed practice, with learning sessions spaced in time to allow for consolidation between sessions. Sleep is critical for memory consolidation, with slow-wave sleep being important for declarative memories and REM sleep being important for procedural memories, making quality sleep an essential complement. Effective learning techniques such as active retrieval through practice tests, elaboration that connects new information with existing knowledge, and interleaving that mixes practice of related skills can enhance effects. Supplementation with choline, a precursor to acetylcholine, or with magnesium, which modulates NMDA receptors, may be synergistic.

Support for emotional regulation and resilience to stress

This protocol is designed for individuals seeking to support the hippocampus' ability to appropriately regulate the stress axis, promote emotional balance, and contribute to resilience through structural restoration of the hippocampus that may be compromised by chronic stress.

• Adaptation phase dosage (days 1-5): Start with 10 mg (1 capsule) once daily in the morning with breakfast. This low initial dose allows neuroendocrine systems to gradually adjust to NSI-189 modulation without causing sudden changes in feedback of the hypothalamic-pituitary-adrenal axis.

• Maintenance dosage (from day 6): Increase to 20-30 mg daily. The recommended protocol is 10 mg (1 capsule) in the morning with breakfast and 10-20 mg (1-2 capsules) at midday with lunch. This dosage provides continuous support for hippocampal function throughout the day when stress responses are most frequently elicited and when emotional regulation is most needed.

• Dosage for periods of heightened stress: During periods of particularly intense stress, such as significant life transitions, periods of high work demands, or challenging personal circumstances, the dosage may be temporarily increased to 30–40 mg daily, divided into two doses of 15–20 mg (2 capsules per dose), for 8–12 weeks, followed by a gradual return to maintenance dosage. It is important to note that NSI-189 is not an acute stress intervention but rather supports structural and functional processes that unfold over weeks, making it more appropriate for support during prolonged periods of stress than for managing acute stress.

• Administration frequency: Morning administration with breakfast provides support during the day when cortisol is naturally higher following a circadian rhythm with a morning cortical peak, and when social interactions and potentially stressful situations are more likely. A second dose at midday maintains levels throughout the afternoon. Some users who experience difficulty falling asleep when NSI-189 is taken late in the day may benefit from taking a second dose no later than mid-afternoon. Administration with food containing healthy fats may enhance absorption of the lipophilic compound.

• Cycle duration: The effects on emotional regulation and stress resilience typically emerge gradually during the first 4–8 weeks of use as structural changes in the hippocampus develop. This protocol can be followed for 16–24 weeks to allow for complete restoration of hippocampal structure and function that may have been compromised by prior chronic stress. After this period, a 3–4 week break can be implemented during which learned stress management techniques and achieved structural changes can be maintained. The protocol can be resumed with maintenance doses if stress continues or if stressful periods are anticipated. For individuals with a history of prolonged chronic stress, longer cycles of 6–9 months of use with 4–6 week breaks may be appropriate, given that complete reversal of stress-induced structural changes may require extended time.

• Special considerations: NSI-189 provides neurobiological support for stress regulation but is most effective when combined with active stress management strategies, including mindfulness-based stress reduction techniques that have been shown to modulate hypothalamic-pituitary-adrenal axis activity; regular exercise, which reduces baseline cortisol and improves stress responses; breathing and relaxation techniques that activate the parasympathetic nervous system; cognitive behavioral therapy or related therapies that provide tools to modify stress-related thought and behavior patterns; sleep optimization, which is critical for emotional regulation, as sleep deprivation exacerbates stress reactivity; and building social support, which is a powerful buffer against stress. Supplementation with adaptogens such as ashwagandha, which modulates cortisol, or with magnesium, which has calming effects on the nervous system, may be complementary. It is important that individuals experiencing severe stress or who are in crisis seek appropriate professional support, with NSI-189 being a complement to comprehensive interventions rather than a substitute.

Spatial memory optimization and navigation function

This protocol is geared towards individuals seeking to support hippocampal function in spatial information processing, cognitive mapping of the environment, and navigation, functions that are particularly dependent on hippocampal integrity and neurogenesis in the dentate gyrus.

• Adaptation phase dosing (days 1-5): Start with 10 mg (1 capsule) once daily in the morning with breakfast. This gradual introduction allows hippocampal circuits involved in spatial processing to adjust to NSI-189 modulation.

• Maintenance dosage (from day 6): Increase to 20-30 mg daily, divided into two doses. The standard protocol is 10 mg (1 capsule) in the morning and 10-20 mg (1-2 capsules) at midday. This dosage supports the function of place cells in the hippocampus, which encode specific positions in the environment and are critical for spatial navigation.

• Dosage during intensive space training: For individuals involved in activities requiring complex space navigation, such as pilots, professional drivers, or athletes in orienteering sports, or during periods of learning complex new environments, the dosage may be increased to 30-40 mg daily during an intensive training period of 8-12 weeks. The suggested distribution is two doses of 15-20 mg (2 capsules per dose) spaced throughout the day.

• Administration frequency: For goals related to spatial memory and navigation, it may be beneficial to take a morning dose before periods of exploration or navigation practice to ensure that neurobiological support is present during spatial information encoding. Administration with breakfast provides a base for the day's activity. Studies have shown that active exploration of novel environments stimulates hippocampal neurogenesis, suggesting potential synergy between NSI-189 and active spatial navigation experience.

• Cycle duration: This protocol can be followed for 12–16 weeks to allow neurogenesis and dendritic remodeling in the hippocampus to improve spatial representations. For individuals learning complex new geography, such as during relocation to a new city, the usage period can coincide with the initial learning phase of the environment for the first 3–4 months, followed by a 2–4 ​​week break once familiarity with the environment is established. The cycle can be repeated if further relocation or a new complex environment needs to be learned. For ongoing support of spatial function, particularly in older adults where spatial function may decline, cycles of 12 weeks of use followed by 2–3 weeks of rest may be appropriate.

• Special considerations: Spatial memory and navigation are skills that improve with active practice. The effectiveness of NSI-189 is maximized when combined with active exploration of environments, navigation practice without relying exclusively on GPS (which can reduce dependence on endogenous hippocampal spatial representations), spatial memory exercises such as recalling routes or object locations, and activities requiring spatial reasoning such as spatial puzzles or navigation video games. Aerobic exercise, particularly in novel or complex environments, can be doubly beneficial by stimulating neurogenesis while providing spatial experience. Virtual reality can provide controlled environments for spatial navigation training. It is noteworthy that hippocampal spatial function shows substantial individual variation, with some people being naturally better spatial navigators, and that training can improve function even in people who initially have difficulty with spatial tasks.

Support for pattern separation and formation of distinctive memories

This protocol is designed for people seeking to improve the dentate gyrus' ability to perform pattern separation, which is the process of making similar experiences more distinct in their neural representations, supporting the formation of detailed memories and reducing interference between similar memories.

• Adaptation phase dosage (days 1-5): Start with 10 mg (1 capsule) once daily in the morning with breakfast. This initial dose allows the granule neuron population in the dentate gyrus, including mature neurons and immature neurons of adult neurogenesis, to adjust to NSI-189 modulation.

• Maintenance dosage (from day 6): Increase to 20-30 mg daily, divided into two doses of 10-15 mg each, taken with breakfast and lunch. This dosage supports both the survival of newly born granule neurons, which are particularly important for pattern separation because they have greater excitability and can be preferentially recruited to representations of similar but distinct experiences, and the optimal function of mature neurons.

• Advanced dosage (for high discrimination demands): For individuals involved in activities requiring fine discrimination between similar stimuli, such as professional tasters who must distinguish between subtly different wines or coffees, musicians who must discriminate between close tones, or any profession requiring detailed memory of similar individuals or objects, the dose may be increased to 30-40 mg daily during periods of intensive training or practice, divided into two doses of 15-20 mg.

• Administration frequency: Morning and midday administration provides support during memory encoding periods throughout the day. For tasks requiring pattern separation, such as learning to recognize similar faces or discriminating between subtly different stimuli, taking doses 30–60 minutes before practice or exposure periods may optimize compound availability during encoding. Administration with food may promote consistent absorption.

• Cycle duration: The effects on pattern separation depend particularly on the integration of newly born neurons into dentate gyrus circuits, a process that takes several weeks. This protocol can be followed for 12–20 weeks to allow a cohort of new neurons to be born, mature, and functionally integrate. After this period, a 2–4 ​​week break can be implemented, followed by a return to the protocol if continuous maintenance of optimal pattern separation function is desired. For individuals whose work critically depends on fine discrimination, longer cycles of 16–24 weeks with shorter 2-week breaks may be appropriate.

• Special considerations: Pattern separation is enhanced by deliberate practice of discriminating between similar stimuli. The effectiveness of NSI-189 can be maximized through perceptual discrimination training, practice recalling specific details that distinguish similar experiences, and elaborative encoding techniques that emphasize distinctive features. Spatial memory tasks requiring discrimination between nearby locations or similar spatial configurations are particularly dependent on hippocampal pattern separation. Acute stress can enhance memory consolidation, but chronic stress compromises pattern separation, making stress management important. Adequate sleep is critical, as memory consolidation during sleep may depend on appropriate pattern separation during initial encoding. Novelty and variation in experiences may promote neurogenesis that underlies pattern separation, suggesting that exposure to novel environments and experiences may be synergistic with the effects of NSI-189.

Did you know that NSI-189 is one of the few compounds investigated that has shown the ability to stimulate neurogenesis in the adult hippocampus, promoting the growth of new neurons in a brain region that was traditionally considered incapable of regenerating after development?

The hippocampus is a seahorse-shaped brain structure located in the medial temporal lobe that plays critical roles in the formation of declarative memories, spatial navigation, and the regulation of emotional responses. For decades, neuroscience held that the adult brain was incapable of generating new neurons, with all neurons being established during prenatal and early postnatal development. However, groundbreaking discoveries in recent years have demonstrated that adult neurogenesis, the birth of new neurons, continues to occur in specific regions of the adult brain, with the dentate gyrus of the hippocampus being one of the most active sites. NSI-189 has been specifically investigated for its ability to stimulate this hippocampal neurogenesis, promoting the proliferation of neural progenitor cells residing in the subgranular zone of the dentate gyrus, facilitating their differentiation into mature, functional neurons, and supporting their integration into existing neural circuits through the formation of appropriate synaptic connections. Preclinical studies using cell-marking techniques and histological analysis have shown that treatment with NSI-189 increases the number of newly formed cells in the hippocampus that express neuronal markers, suggesting the promotion of neurogenesis. This ability to stimulate the growth of new neurons in the adult brain is extraordinarily rare among pharmacological compounds, with most existing interventions focusing on protecting existing neurons rather than generating new ones, making the proposed mechanism of NSI-189 unique and fascinating from a neuroscience perspective.

Did you know that NSI-189 has been investigated for its ability to increase hippocampal volume, not only through neurogenesis but also by promoting dendritic arborization and the formation of new synapses that expand the connectivity of neural networks?

Beyond simply increasing the number of neurons, NSI-189 has been studied for its effects on the structural architecture of the hippocampus, including the promotion of dendritic growth. Dendrites, which are branching extensions of neurons that receive synaptic signals from other neurons, can extend and branch more extensively, increasing the surface area available for synapse formation. The compound has also been investigated for its effects on spinogenesis, the formation of dendritic spines—small protrusions on dendrites where most excitatory synapses are formed—with more spines signifying a greater capacity for neuronal communication. Structural neuroimaging studies using magnetic resonance imaging have investigated whether treatment with NSI-189 results in measurable changes in hippocampal volume in humans, with some studies reporting increases in hippocampal volume after prolonged treatment. However, interpretation of these findings requires careful consideration of multiple methodological factors. The molecular mechanisms by which NSI-189 could promote these structural changes include modulation of neurotrophic factors, which are proteins that support neuronal growth, survival, and differentiation; modulation of intracellular signaling pathways that regulate neuronal cytoskeleton growth necessary for neurite extension; and possibly effects on the regulation of genes that control the expression of synaptic structural proteins. The potential outcome is an expansion of the hippocampus's computational capacity through an increase in the number of processing elements (neurons) and in the connectivity between them (synapses), which could theoretically translate into improved hippocampal-dependent functions, including memory formation and spatial information processing.

Did you know that NSI-189 has shown in research the ability to modulate levels of brain-derived neurotrophic factor (BDNF), a critical protein that acts as a molecular fertilizer for neurons, supporting their growth, survival, and synaptic plasticity?

BDNF is a member of the neurotrophin family, which are secreted proteins that bind to specific receptors on neurons, promoting multiple effects critical for healthy brain function. BDNF binds to the TrkB receptor, a tyrosine kinase receptor that, when activated by BDNF binding, initiates intracellular signaling cascades. These cascades promote neuronal survival by activating anti-apoptotic pathways, promote neurite growth and synapse formation by modulating the cytoskeleton, facilitate synaptic plasticity (the cellular basis of learning and memory) by affecting the efficiency of synaptic transmission, and support adult neurogenesis by affecting the proliferation and differentiation of neural progenitor cells. BDNF levels in the brain can be influenced by multiple factors, including physical exercise, which increases BDNF, particularly in the hippocampus; chronic stress, which reduces BDNF; and certain pharmacological compounds. NSI-189 has been investigated for its ability to increase BDNF expression in the hippocampus, with preclinical studies showing upregulation of BDNF messenger RNA and BDNF protein after treatment. This increase in BDNF could be the mechanism by which NSI-189 promotes neurogenesis and hippocampal structural enhancement, given that BDNF is necessary for the survival and proper differentiation of newly born neurons. Modulation of BDNF levels by NSI-189 could also contribute to effects on synaptic plasticity and cognitive function, since BDNF is critical for long-term potentiation (LTP), a form of synaptic plasticity where synaptic transmission efficiency is permanently increased, and LTP is considered a cellular mechanism underlying memory formation.

Did you know that NSI-189 was specifically designed using medicinal chemistry techniques to efficiently cross the blood-brain barrier, allowing it to reach appropriate concentrations in brain tissue to exert its proposed neurogenic effects?

The blood-brain barrier is a highly selective interface composed of brain endothelial cells held together by tight junctions, creating a physical barrier, along with astrocytes and pericytes that provide structural and regulatory support. This barrier protects the brain from pathogens, toxins, and fluctuations in blood composition, but it also presents a significant challenge for the development of compounds that need to act on the central nervous system, since most molecules cannot cross this barrier. For a compound to cross the blood-brain barrier, it must meet certain physicochemical criteria, including a relatively low molecular weight (typically less than 400–500 daltons), appropriate lipophilicity (measured by a partition coefficient that allows the molecule to dissolve in the lipid bilayer of membranes but not be so lipophilic as to bind nonspecifically to plasma proteins), and a limited number of hydrogen bond donor and acceptor groups, according to Lipinski's rule. NSI-189 was designed with these properties in mind. It is a small molecule with a molecular weight of approximately 366 daltons, exhibiting an appropriate balance between lipophilicity and hydrophilicity, allowing it to cross the blood-brain barrier via passive diffusion. Pharmacokinetic studies have confirmed that after oral administration, NSI-189 reaches measurable concentrations in the brain, with a high brain-to-plasma ratio indicating adequate penetration. This ability to reach its site of action in the central nervous system is critical for its proposed neurogenic effects, distinguishing NSI-189 from compounds that may have in vitro activity but cannot access the brain in vivo.

Did you know that the exact mechanism of action of NSI-189 is not yet fully characterized, but research suggests that it may modulate multiple intracellular signaling pathways, including the ERK, AKT, and mTOR pathways, which are critical for neuronal growth and survival?

Despite observed effects of NSI-189 on neurogenesis and hippocampal volume, the precise molecular targets and signaling mechanisms by which the compound exerts these effects remain an active area of ​​research. Mechanistic studies have investigated multiple intracellular signaling pathways known to regulate neuronal growth, survival, and differentiation. The ERK (extracellular signal-regulated kinase) pathway is a component of the MAP kinase signaling pathway that transduces signals from cell surface receptors into the nucleus, regulating the transcription of genes involved in cell proliferation, differentiation, and survival, with ERK activation being necessary for neurogenesis and synaptic plasticity. The AKT (also known as protein kinase B) pathway is a serine-threonine kinase that is activated downstream of insulin receptors and growth factor receptors, promoting cell survival by phosphorylating and inhibiting pro-apoptotic proteins, promoting protein synthesis, and regulating glucose metabolism. The mTOR (mammalian target of rapamycin) pathway is a kinase that functions as a central sensor of nutrient and growth factor availability, regulating protein synthesis, cell growth, and autophagy. In vitro studies have shown that treatment with NSI-189 can result in increased phosphorylation of ERK, AKT, and mTOR pathway components in cultured neurons, suggesting activation of these pathways. However, the upstream receptor or molecular target to which NSI-189 directly binds remains definitively unidentified, with possibilities including direct binding to a yet-to-be-identified receptor, modulation of ion channels, or effects on intracellular signaling through mechanisms that do not involve traditional receptor binding.

Did you know that NSI-189 has been studied in phase I and phase II clinical trials in humans, demonstrating an acceptable safety profile and reasonable tolerability at the doses investigated, with adverse events generally being mild to moderate?

The clinical development of NSI-189 has included multiple human trials evaluating the compound's safety, tolerability, pharmacokinetics, and preliminary efficacy. Phase I studies, the first human trials focused primarily on safety and pharmacokinetics, involved administering NSI-189 to healthy volunteers at escalating doses to characterize the compound's absorption, distribution, metabolism, and excretion, as well as to identify any dose-limiting toxicities. These studies established that NSI-189 can be administered orally with appropriate absorption resulting in systemic exposure, that metabolism occurs primarily in the liver via cytochrome P450 enzymes, and that elimination occurs through renal and biliary excretion. Phase II studies evaluating preliminary efficacy in populations with specific conditions have administered NSI-189 over several weeks, characterizing effects on neuroimaging measures, including hippocampal volume, on neuropsychological batteries assessing cognitive function and other parameters, and continuing safety monitoring. Adverse events reported in these studies have primarily included mild gastrointestinal symptoms such as nausea, headache (typically mild and transient), insomnia in some participants, particularly with nighttime dosing, and occasionally effects on sleep or energy. Discontinuations due to adverse events have been relatively infrequent, suggesting that overall tolerability is acceptable. It is important to note that these clinical studies were conducted under close medical supervision with careful monitoring, and that use outside of a clinical research context should consider limitations in fully understanding the long-term safety profile.

Did you know that NSI-189 could modulate synaptic plasticity in the hippocampus by affecting NMDA and AMPA receptors, which are glutamate receptors critical for long-term potentiation, the cellular mechanism underlying memory formation?

Synaptic plasticity refers to the ability of synapses to strengthen or weaken in response to neuronal activity, and is fundamental for learning and memory. Long-term potentiation (LTP) is a form of synaptic plasticity where high-frequency stimulation of a neuronal pathway results in lasting strengthening of synaptic transmission, while long-term depression (LTD) is the opposite, where low-frequency stimulation results in weakening of transmission. Glutamate receptors, particularly NMDA (N-methyl-D-aspartate) and AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate) receptors, are critical for LTP in the hippocampus. NMDA receptors function as coincidence detectors that only allow calcium influx when two conditions are met simultaneously: glutamate is bound to the receptor, and the postsynaptic membrane is sufficiently depolarized to remove magnesium blockage from the channel. This calcium influx triggers signaling cascades that strengthen synapses. AMPA receptors mediate most fast excitatory synaptic transmission, and their insertion into the postsynaptic membrane during LTP is a key mechanism of synaptic strengthening. NSI-189 has been investigated for its effects on the expression and function of these receptors, with some studies suggesting that treatment may increase the expression of NMDA and AMPA receptor subunits in the hippocampus and may modulate receptor trafficking to the synaptic membrane. These effects on glutamate receptors could contribute to enhanced synaptic plasticity and could be a mechanism by which NSI-189 might support learning and memory processes that critically depend on hippocampal LTP.

Did you know that NSI-189 has shown in preclinical studies the ability to promote not only neurogenesis in the dentate gyrus of the hippocampus, but also long-term survival of these newborn neurons, supporting their maturation and functional integration into existing circuits?

Adult neurogenesis is a multi-stage process that includes the proliferation of neural progenitor cells in the subgranular zone of the dentate gyrus, differentiation of these cells into neuronal lineages, migration of immature cells into the granular layer, maturation through the development of appropriate neuronal morphology with the extension of axons and dendrites, formation of synapses with pre-existing neurons (both receiving inputs and projecting outputs), and functional integration into existing neural circuits, participating in information processing. A critical challenge in adult neurogenesis is that while many new cells are continuously born, a large proportion of these cells die within the first few weeks after birth through apoptosis if they do not receive appropriate survival signals. It is estimated that only a fraction of newborn cells survive to become functional, mature neurons. Factors that determine whether a newborn neuron survives include neuronal activity (with activated newborn neurons having a higher probability of survival), the availability of neurotrophic factors, particularly BDNF, which provides survival signals, and appropriate integration into circuits, where the formation of synaptic connections is critical for survival. NSI-189 has been investigated not only for its effects on the initial proliferation of progenitor cells, but also for its effects on the survival of newly born neurons during the critical period when many would normally die. Studies using labeling of dividing cells with nucleotide analogs that are incorporated during DNA replication, followed by analyses at later time points, have shown that treatment with NSI-189 increases not only the number of initially labeled cells, but also the number of labeled cells that survive weeks later, suggesting the promotion of cell survival in addition to proliferation.

Did you know that NSI-189 could modulate glutamatergic and GABAergic neurotransmission in the hippocampus, influencing the balance between excitation and inhibition that is critical for proper function of neuronal networks and for prevention of hyperexcitability?

The hippocampus contains excitatory glutamatergic neurons, which constitute approximately 90% of its neurons and use glutamate as a neurotransmitter, promoting the activation of postsynaptic neurons. It also contains inhibitory GABAergic interneurons, which constitute approximately 10% of its neurons and use GABA as a neurotransmitter, inhibiting postsynaptic neurons. The balance between glutamate-mediated excitation and GABA-mediated inhibition is critical for proper brain function. An imbalance toward excessive excitation can result in hyperexcitability and potentially seizure activity, while an imbalance toward excessive inhibition can compromise information processing and plasticity. NSI-189 has been investigated for its effects on this excitation-inhibition balance through multiple mechanisms. Electrophysiological studies recording the electrical activity of neurons have investigated the effects of NSI-189 on excitatory synaptic transmission mediated by glutamate receptors and on inhibitory synaptic transmission mediated by GABA receptors. Some studies have suggested that NSI-189 may modulate neurotransmitter release from presynaptic terminals, affect the sensitivity of postsynaptic receptors, or modulate the intrinsic excitability of neurons through effects on ion channels that determine neuronal firing properties. Additionally, since adult neurogenesis adds new excitatory neurons to the dentate gyrus, questions remain about how these new neurons affect excitation-inhibition balance, with some evidence suggesting that newly born neurons are initially more excitable than mature neurons but are subsequently integrated into appropriate inhibitory circuits. The effects of NSI-189 on neurotransmission modulation could contribute to its effects on cognitive function and on the regulation of emotional states, which depend on appropriate information processing in hippocampal circuits.

Did you know that NSI-189 has been investigated for its ability to modulate the hypothalamic-pituitary-adrenal (HPA) axis, the neuroendocrine system that coordinates stress responses through cortisol secretion and is intimately connected to the hippocampus?

The HPA axis is a neuroendocrine system that coordinates physiological responses to stress, beginning with the release of corticotropin-releasing hormone (CRH) from the hypothalamus in response to stressors. CRH stimulates the release of adrenocorticotropic hormone (ACTH) from the anterior pituitary gland. ACTH travels through the bloodstream to the adrenal glands, where it stimulates the synthesis and release of glucocorticoids, particularly cortisol in humans. Cortisol has multiple systemic effects, preparing the body for a stress response, including the mobilization of glucose from stores, redistribution of blood flow, and suppression of non-essential functions such as digestion and reproduction. Critically, the HPA axis is under negative feedback regulation, where circulating cortisol inhibits further release of CRH and ACTH to prevent excessive activation. The hippocampus plays a central role in this negative feedback, given its high density of glucocorticoid receptors. Hippocampal neurons detect cortisol levels and send inhibitory signals to the hypothalamus and pituitary gland to suppress the HPA axis. During chronic stress, prolonged exposure to elevated cortisol can have deleterious effects on the hippocampus, including dendritic atrophy, reduced neurogenesis, and eventually a reduction in hippocampal volume, creating a vicious cycle where a damaged hippocampus is less effective at regulating the HPA axis, resulting in chronically elevated cortisol that further damages the hippocampus. NSI-189 has been investigated for its effects on HPA axis function, with the hypothesis being that restoring hippocampal structure and function by promoting neurogenesis could improve negative feedback on the HPA axis, resulting in more appropriate regulation of cortisol secretion.

Did you know that research has shown that NSI-189 can modulate the expression of genes related to neuronal plasticity, including genes that encode cytoskeleton proteins, synaptic proteins, and transcription factors that regulate neuronal differentiation?

Gene expression is the process by which information encoded in DNA is transcribed into messenger RNA and translated into proteins that perform cellular functions, with gene expression regulation being a fundamental mechanism by which cells respond to environmental signals and modulate their function. In neurons, the expression of specific genes is critical for multiple aspects of neuronal function, including the development of appropriate neuronal morphology, synapse formation and maintenance, and synaptic plasticity that underlies learning. NSI-189 has been investigated for its effects on gene expression profiles in the hippocampus using techniques such as DNA microarrays or RNA sequencing, which allow for the simultaneous quantification of messenger RNA levels for thousands of genes. These studies have identified multiple genes whose expression is modulated by NSI-189 treatment. Genes related to the cytoskeleton, including those encoding tubulins, actins, and microtubule-associated proteins, are important because the cytoskeleton is necessary for neurite growth during neuronal development and for the maintenance of dendritic and axonal morphology. Genes related to synaptic function, including those encoding neurotransmitter receptors, postsynaptic scaffolding proteins, and proteins involved in synaptic vesicle release, are critical for synapse formation and function. Genes encoding transcription factors—proteins that bind to specific DNA sequences and regulate the transcription of other genes—are particularly interesting because they can amplify effects by controlling the expression of multiple downstream genes. The modulation of these genes' expression by NSI-189 provides potential molecular mechanisms by which this compound could promote neurogenesis, dendritic growth, and synaptic formation, as observed in functional and structural studies.

Did you know that NSI-189 may have effects on mitochondrial function in neurons, supporting cellular energy production that is critical for metabolically demanding processes such as neurogenesis, dendritic growth, and synaptic transmission?

Neurons have extraordinarily high energy demands. Maintaining ion gradients across membranes via ATP-dependent pumps such as Na+/K+-ATPase consumes approximately 50% of neuronal ATP. Synaptic transmission requires energy for the synthesis, packaging, and release of neurotransmitters, as well as for the recycling of synaptic components. Growth processes, including neurite extension and synapse formation, require massive synthesis of membranes and proteins. Mitochondria are organelles that generate the majority of cellular ATP through oxidative phosphorylation, with neurons containing a particularly high density of mitochondria, especially in energy-dense regions such as presynaptic terminals and dendritic spines. Mitochondrial function can be compromised by multiple factors, including oxidative stress, where reactive oxygen species damage mitochondrial components; deficiencies in cofactors required for the respiratory chain; and the accumulation of mitochondrial DNA damage. NSI-189 has been investigated for its effects on mitochondrial function in neurons by measuring parameters such as oxygen consumption, which reflects respiratory chain activity; ATP production; mitochondrial membrane potential, which drives ATP synthesis; and reactive oxygen species generation. Some studies have suggested that NSI-189 may enhance mitochondrial function through mechanisms that could include increased mitochondrial biogenesis (the formation of new mitochondria), improved oxidative phosphorylation efficiency, or reduced mitochondrial oxidative stress. Enhanced mitochondrial function could be particularly relevant for supporting neurogenesis, given that proliferating and differentiating cells have very high energy demands, and could also support synapse maintenance and synaptic plasticity, which are metabolically costly processes.

Did you know that NSI-189 has been investigated for its ability to modulate inflammation in the central nervous system through effects on microglia, the brain's resident immune cells that can exist in pro-inflammatory or anti-inflammatory states?

Microglia are myeloid-derived cells that reside in the central nervous system, functioning as brain macrophages and constituting approximately 10–15% of brain cells. In their basal surveillance state, microglia continuously scan the brain environment by extending and retracting cellular processes, detecting signs of damage, pathogens, or dysfunction. When microglia detect danger signals, they can be activated into a pro-inflammatory phenotype (classically called M1) where they secrete pro-inflammatory cytokines such as TNF-alpha, IL-1β, and IL-6, produce reactive oxygen and nitrogen species, and can phagocytize damaged material. Alternatively, microglia can be activated into an anti-inflammatory or reparative phenotype (classically called M2) where they secrete anti-inflammatory cytokines such as IL-10 and TGF-β, produce neurotrophic factors that support neuronal survival, and aid in the resolution of inflammation and tissue repair. During aging or chronic stress, microglia can become chronically activated in a pro-inflammatory state, secreting inflammatory factors that can damage neurons, inhibit neurogenesis by affecting progenitor cells, and impair synaptic function. NSI-189 has been investigated for its effects on microglial activation using techniques such as immunohistochemistry for markers of microglial activation, measurement of cytokine levels in brain tissue, and gene expression analysis of isolated microglia. Some studies have suggested that treatment with NSI-189 can modulate microglial polarization by reducing markers of a pro-inflammatory phenotype and increasing markers of an anti-inflammatory or reparative phenotype. This modulation of neuronal inflammation could contribute to the neurogenic effects of NSI-189, given that an inflammatory environment inhibits neurogenesis, and could also support neuroprotection and cognitive function, since chronic neuroinflammation compromises neuronal function.

Did you know that NSI-189 could modulate functional connectivity between the hippocampus and other brain regions, including the prefrontal cortex and amygdala, regions that together form networks involved in emotional processing, memory, and executive functions?

The brain functions as a highly interconnected network rather than a collection of independent regions, with complex cognitive and emotional functions emerging from coordinated interactions among multiple brain regions. The hippocampus is anatomically and functionally connected to multiple cortical and subcortical regions: connections with the medial prefrontal cortex, particularly the prelimbic and infralimbic cortex, are involved in memory consolidation, the extinction of fear memories, and the regulation of emotional responses. Connections with the amygdala, a subcortical nucleus critical for processing emotions, particularly fear, are involved in the formation of emotional memories and in modulating memory consolidation based on the emotional valence of experiences. Reciprocal connections between the hippocampus and the entorhinal cortex, which serves as the main gateway between the hippocampus and the neocortex, are critical for processing spatial information and for transferring information between short-term and long-term memory. Functional connectivity between these regions can be assessed using functional neuroimaging techniques such as resting-state functional magnetic resonance imaging (fMRI), which measures temporal correlations in activity between distinct brain regions, reflecting functional communication between them. Studies have investigated whether treatment with NSI-189 modulates patterns of functional connectivity, with the hypothesis being that structural improvement of the hippocampus through neurogenesis could translate into changes in how the hippocampus interacts with other brain regions. Some studies have reported changes in functional connectivity between the hippocampus and prefrontal cortex after treatment with NSI-189, although interpretation of these findings requires careful consideration of methodology and multiple factors.

Did you know that NSI-189 has pharmacokinetic properties that include a relatively short elimination half-life requiring multiple daily doses to maintain therapeutic levels, and that it is primarily metabolized by hepatic cytochrome P450 enzymes?

Pharmacokinetics describes how the body processes a drug compound through four main processes: absorption, where the compound enters systemic circulation from the administration site; distribution, where the compound is transported by the blood and distributed among tissues; metabolism, where the compound is chemically modified, typically in the liver, to facilitate elimination; and excretion, where the compound and its metabolites are eliminated from the body, typically by the kidneys in urine or by the liver in bile. When administered orally, NSI-189 is absorbed from the gastrointestinal tract, with moderate oral bioavailability—the fraction of the dose that reaches systemic circulation—reflecting incomplete absorption and first-pass metabolism in the liver. Once in circulation, NSI-189 is distributed to multiple tissues, including the brain, as previously discussed. NSI-189 metabolism occurs primarily in the liver via cytochrome P450 enzymes, particularly isoforms such as CYP3A4, one of the most abundant enzymes and one that metabolizes a large proportion of drugs. This metabolism generates multiple metabolites that are more hydrophilic than the parent compound, facilitating their renal excretion. The elimination half-life of NSI-189, which is the time required for plasma concentrations to decrease by half, is relatively short, typically in the range of 8–12 hours, meaning that the compound is relatively rapidly eliminated from the body. This relatively short half-life has implications for dosing regimens, with two- or three-times-daily dosing typically being necessary to maintain relatively constant plasma concentrations during the dosing interval. Potential drug interactions must be considered, since metabolism by CYP3A4 means that compounds that inhibit this enzyme, such as certain antifungals or grapefruit juice, could increase NSI-189 concentrations, while compounds that induce CYP3A4, such as St. John's wort, could decrease concentrations.

Did you know that NSI-189 has been investigated using advanced neuroimaging techniques such as magnetic resonance spectroscopy, which can measure concentrations of brain metabolites, including N-acetylaspartate, a marker of neuronal integrity?

Magnetic resonance spectroscopy (MRS) is a neuroimaging technique that allows for the non-invasive quantification of specific metabolite concentrations in defined brain regions. While conventional structural magnetic resonance imaging provides anatomical images based on proton signals in water and fat, MRS can detect proton signals in specific metabolites that are present at much lower concentrations but provide information about brain metabolism and chemistry. Metabolites that can be quantified by MRS include N-acetylaspartate (NAA), a marker of neuronal density and viability, with reduced NAA levels suggesting neuronal loss or dysfunction; creatine, which is involved in energy metabolism and is frequently used as an internal reference because its levels are relatively stable; choline, which is involved in membrane synthesis and signaling, with increased levels potentially indicating increased membrane turnover; myo-inositol, a marker of glial cells, particularly astrocytes; and glutamate and glutamine, the main excitatory neurotransmitter and its precursor, respectively. Studies of NSI-189 have used MRS to investigate whether treatment results in changes in these brain metabolites, particularly in the hippocampus. Some studies have reported increases in hippocampal NAA levels after NSI-189 treatment, which has been interpreted as a potential indicator of improved neuronal integrity or increased neuronal density consistent with proposed neurogenic effects. However, interpreting metabolite changes measured by MRS requires caution, given that multiple factors can influence metabolite levels and correlations between metabolite changes and changes in neuronal function are not always direct.

Did you know that NSI-189 could modulate the expression of neurotrophin receptors, including the TrkB receptor, which is a high-affinity receptor for BDNF, potentially amplifying neurotrophic signaling that supports neuronal survival and growth?

Neurotrophins are a family of growth factors that include nerve growth factor (NGF), BDNF, neurotrophin-3 (NT-3), and neurotrophin-4 (NT-4). These factors bind to two types of receptors: Trk receptors (tropomyosin receptor kinase), which are high-affinity receptors specific for different neurotrophins (TrkA being the receptor for NGF, TrkB being the receptor for BDNF and NT-4, and TrkC being the receptor for NT-3), and p75NTR receptors, which are low-affinity receptors that bind all neurotrophins. The binding of neurotrophins to Trk receptors activates intracellular signaling cascades, including MAP kinase, PI3K-AKT, and phospholipase C-gamma pathways, which promote neuronal survival, growth, and differentiation. The expression of Trk receptors in neurons determines their ability to respond to neurotrophins, with neurons expressing high levels of TrkB being more responsive to BDNF. NSI-189 has been investigated for its effects on the expression of neurotrophin receptors, particularly TrkB, with the hypothesis that increased TrkB expression could amplify endogenous BDNF signaling, creating a synergistic effect where NSI-189 increases both BDNF levels and the expression of its receptor, TrkB. Studies have used techniques such as Western blot to quantify TrkB protein levels, quantitative PCR to measure TrkB messenger RNA levels, and immunohistochemistry to visualize TrkB expression in different cell types and brain regions. Some studies have reported that NSI-189 treatment increases TrkB expression in the hippocampus, which could enhance neurotrophic signaling. Additionally, NSI-189 may modulate post-translational processing of TrkB, including phosphorylation and trafficking of the receptor to the plasma membrane, where it can interact with extracellular BDNF, influencing neuronal sensitivity to neurotrophic signaling.

Did you know that NSI-189 has been investigated for its effects on sleep architecture, including potential effects on REM sleep and slow-wave sleep, which are critical stages for memory consolidation and brain restoration?

Sleep is not a uniform state but consists of multiple stages that cycle throughout the night: non-REM sleep, which includes stages 1 and 2 (light sleep) and stages 3 and 4 (slow-wave sleep, also called deep sleep), characterized by high-amplitude delta waves on electroencephalogram; and REM (rapid eye movement) sleep, characterized by cortical desynchronization similar to wakefulness, muscle atonia, and intense dreaming activity. Different sleep stages have distinct functions: slow-wave sleep is critical for consolidating declarative memories through the replay of neuronal activity patterns that occurred during wakefulness, particularly in the dialogue between the hippocampus and cortex; for cerebral metabolic restoration, including the replenishment of astrocytic glycogen; and for clearing brain metabolites via the glymphatic system. REM sleep is important for consolidating procedural memories, for emotional processing, and for integrating experiences. The hippocampus plays critical roles in memory consolidation during sleep by generating high-frequency oscillations called ripple waves. These ripples occur during slow-wave sleep and are associated with the replay of neuronal activity sequences that encode experiences. They coordinate the transfer of information from the hippocampus to the neocortex for long-term storage. NSI-189 has been investigated for its effects on sleep architecture using polysomnography, which simultaneously records EEG, electromyography, and eye movements, allowing for the classification of sleep stages. Some studies have reported that NSI-189 can modulate sleep latency (the time required to fall asleep), affect the proportion of time spent in different sleep stages, or modulate EEG characteristics during sleep. These effects on sleep could be relevant to cognitive functions, given that adequate sleep is critical for consolidating memories formed during wakefulness, and NSI-189-induced changes in hippocampal structure could influence memory processing during sleep.

Did you know that NSI-189 could have effects on neurogenesis in brain regions beyond the hippocampus, potentially including the subventricular zone, which is another neurogenic niche in the adult brain that generates neurons that migrate to the olfactory bulb?

While the hippocampus, specifically the dentate gyrus, is the most studied site of adult neurogenesis in mammals, another major neurogenic niche in the adult brain is the subventricular zone surrounding the lateral ventricles. In this region, neural progenitor cells called type B cells, which have astrocyte-like characteristics, generate transient amplification type C cells, which are rapidly proliferating progenitors. These type C cells then generate type A neuroblasts that migrate long distances via the rostral migrating stream to the olfactory bulb, where they differentiate into granular and periglomerular interneurons that are integrated into olfactory processing circuits. In humans, neurogenesis in the subventricular zone appears to decline dramatically after childhood, with ongoing debate about whether significant subventricular neurogenesis persists into adult humans, although it does persist robustly in many other mammalian species throughout adulthood. In addition to these two main neurogenic niches, there is conflicting evidence regarding neurogenesis in other brain regions, including the cortex, amygdala, and hypothalamus, with most evidence suggesting that if neurogenesis occurs in these regions in adults, it is at very low levels. NSI-189 has been primarily investigated for its effects on hippocampal neurogenesis, but some studies have explored whether the compound has effects on cell proliferation in the subventricular zone or other regions. The mechanisms by which NSI-189 promotes neurogenesis in the hippocampus, such as modulation of neurotrophic factors or activation of signaling pathways that regulate proliferation and differentiation, could theoretically also operate in other neurogenic niches, although the regional specificity of effects depends on the expression of NSI-189 molecular targets and the specific cellular environment of different brain regions.

Did you know that NSI-189 has been investigated in combination with other interventions including cognitive-behavioral therapy, exercise, or other nutraceutical compounds, exploring whether synergistic effects can enhance benefits on brain function and well-being?

The concept of multimodal interventions recognizes that complex brain function and well-being are influenced by multiple interacting factors, suggesting that combining multiple complementary interventions could result in greater benefits compared to any single intervention. Physical exercise, particularly aerobic exercise, has well-established effects on the brain, including increased hippocampal neurogenesis through multiple mechanisms, such as increased BDNF, improved cerebral blood flow, and reduced inflammation. Psychological therapies, such as cognitive behavioral therapy, can modify thought and behavior patterns, modulate activity in brain circuits, including the prefrontal cortex and amygdala, and indirectly influence brain structure through effects on stress and health behaviors. Nutritional interventions, including adequate intake of specific nutrients such as omega-3 fatty acids, B vitamins, and antioxidants, support brain function through multiple mechanisms. Other compounds, such as NAD+ precursors that enhance mitochondrial energy metabolism or sirtuin activators, may have complementary effects with NSI-189. The rationale for combining NSI-189 with these interventions is that while NSI-189 might promote structural changes in the hippocampus through neurogenesis, other interventions might modulate the function of neural circuits, provide necessary metabolic cofactors, or create an optimal neurochemical environment for the expression of NSI-189's effects. Studies have begun to explore these combinations, although evidence remains preliminary. A challenge in studies of combined interventions is the complexity of experimental design and interpretation, given that interactions between interventions can be additive, where combined effects equal the sum of individual effects; synergistic, where combined effects exceed the sum of individual effects; or antagonistic, where one intervention interferes with another.

Did you know that NSI-189 could modulate the expression of genes related to the circadian clock in the hippocampus, potentially influencing local circadian rhythms that coordinate multiple aspects of hippocampal function with the day-night cycle?

Circadian rhythms are approximately 24-hour oscillations in physiological and behavioral processes generated by molecular clocks present in virtually all cells. The master circadian clock is located in the suprachiasmatic nucleus of the hypothalamus and is synchronized by ambient light, but peripheral clocks exist in all tissues, including the brain, where different brain regions have their own local circadian rhythms. The molecular mechanism of the circadian clock involves transcriptional-translational feedback loops where the transcription factors CLOCK and BMAL1 activate the expression of Period (PER) and Cryptochrome (CRY) genes, and PER and CRY proteins subsequently inhibit CLOCK-BMAL1 activity, creating oscillation. The hippocampus exhibits circadian rhythms in multiple parameters, including clock gene expression, glucocorticoid secretion (which peaks during the sleep-wake transition), neurogenesis (where progenitor cell proliferation shows circadian variation), and cognitive function (where memory and learning show time-of-day variations). Disruption of circadian rhythms through chronic desynchronization, such as that which occurs in shift work or chronic jet lag, can have adverse effects on hippocampal function, including impaired neurogenesis and cognitive function. NSI-189 has been investigated for its effects on the expression of circadian clock genes in the hippocampus, with some studies evaluating whether treatment modulates messenger RNA or protein levels of clock components. Effects on the circadian clock could be relevant to hippocampal function, given that appropriate temporal coordination of cellular processes with the day-night cycle can optimize function, and could also be relevant to the effects of NSI-189 on sleep and circadian mood patterns, which may be partially regulated by the hippocampus.

Stimulation of hippocampal neurogenesis and neuronal regeneration

NSI-189 has been specifically investigated for its unique ability to promote the birth of new neurons in the hippocampus, a brain region critical for memory, learning, and emotional processing. Unlike most compounds that focus on protecting existing neurons, NSI-189 works by stimulating neural progenitor cells residing in the dentate gyrus of the hippocampus to divide and differentiate into mature, functional neurons. This process of adult neurogenesis, which naturally declines with age and chronic stress, can be supported through NSI-189 supplementation. Research has shown that the compound not only promotes the initial proliferation of these progenitor cells but also supports the long-term survival of newly formed neurons during the critical period when many would normally die. Furthermore, NSI-189 contributes to the functional integration of these new neurons into existing circuits by supporting the formation of appropriate synaptic connections. This neuronal regeneration process is especially relevant given that the hippocampus can undergo structural changes in response to prolonged stress and aging, and the ability to promote the growth of new neurons represents a regenerative rather than merely protective approach. Stimulation of neurogenesis by NSI-189 could potentially lead to improvements in the ability to form new memories, cognitive flexibility to adapt to new situations, and emotional resilience in the face of challenges, although individual responses may vary considerably.

Expansion of hippocampal volume and improvement of neuronal architecture

Beyond simply increasing the number of neurons, NSI-189 has been studied for its ability to promote broader structural changes in the hippocampus, including an expansion of the overall volume of this brain region. Neuroimaging studies have investigated whether NSI-189 treatment results in measurable increases in hippocampal volume, with some studies reporting detectable changes after several weeks of continuous use. This volumetric expansion is not solely due to an increase in the number of neurons, but also to the promotion of dendritic arborization, the process by which neuronal dendrites extend and branch more extensively, creating a denser and more complex network. Dendrites are the structures that receive signals from other neurons, so greater dendritic branching means a greater capacity to establish synaptic connections and process information. NSI-189 also promotes the formation of dendritic spines, which are small protrusions where most excitatory synapses form, thereby increasing neural connectivity. Additionally, the compound may support axon thickening and proper myelination, processes that improve the speed and efficiency of signal transmission between neurons. These structural changes represent a real expansion of the hippocampus's computational capacity, potentially enabling more robust memory processing, better encoding of spatial experiences, and a greater ability to distinguish between similar experiences—a function known as pattern separation that is critical for detailed episodic memory.

Increased neurotrophic factors that nourish and protect neurons

NSI-189 has been investigated for its ability to increase levels of brain-derived neurotrophic factor (BDNF), a protein that acts as a molecular fertilizer for neurons, supporting their growth, survival, and optimal function. BDNF is critical for multiple processes in the brain: it promotes the survival of existing neurons by activating pathways that prevent programmed cell death, stimulates the growth of new connections between neurons by facilitating synapse formation, supports synaptic plasticity—the ability of synapses to strengthen or weaken in response to activity and which underlies learning and memory—and is necessary for the differentiation and maturation of newly born neurons during neurogenesis. BDNF levels in the brain can decrease in response to chronic stress, aging, and physical inactivity, compromising neuronal health. NSI-189's ability to increase BDNF expression, particularly in the hippocampus where its effects are most pronounced, provides a mechanism by which the compound may exert neuroprotective and plasticity-promoting effects. This increase in BDNF not only benefits newly formed neurons through NSI-189-stimulated neurogenesis, but also supports existing neurons, creating a more favorable neurochemical environment for optimal brain function. BDNF is also involved in regulating mood and stress responses, with appropriate levels contributing to emotional well-being, suggesting that the effects of NSI-189 on BDNF could have benefits that extend beyond cognition to emotional balance.

Improvement of synaptic plasticity and optimization of learning

Synaptic plasticity, the ability of connections between neurons to change in response to experience, is the fundamental cellular mechanism underlying learning, memory, and the brain's adaptation to new circumstances. NSI-189 has been investigated for its ability to enhance this synaptic plasticity, particularly in the hippocampus, where long-term potentiation (LTP), a specific form of long-lasting synaptic strengthening, is critical for the formation of new memories. The compound can modulate the function of glutamate receptors, specifically NMDA and AMPA receptors, which are essential for the induction and expression of LTP. NMDA receptors function as coincidence detectors that only allow calcium influx when two conditions are met simultaneously: glutamate is bound to the receptor, and the postsynaptic membrane is sufficiently depolarized. This calcium influx triggers signaling cascades that strengthen the synapse. NSI-189 can increase the expression of subunits of these receptors and facilitate their trafficking to synapses, thereby optimizing plasticity mechanisms. Furthermore, by promoting the growth of dendritic spines where synapses form, and by increasing dendritic arborization, which provides more potential sites for synapse formation, NSI-189 expands the brain's physical capacity to form new connections. This enhancement of synaptic plasticity could translate into greater ease in acquiring new skills, retaining important information, adapting to changing environments, and maintaining the cognitive flexibility that allows switching between different tasks or mental perspectives.

Support for cognitive function and memory abilities

Given the multiple mechanisms by which NSI-189 influences hippocampal structure and function, the compound has been investigated for its potential to support various aspects of cognitive function. The hippocampus is particularly important for the formation of declarative memories, which include both episodic memories of specific personal events and semantic memories of facts and concepts. By promoting hippocampal neurogenesis, NSI-189 may support the encoding of new memories, the process by which experiences are transformed into stable memory traces. Pattern separation, a specialized function of the hippocampal dentate gyrus where neurogenesis occurs, allows us to distinguish between similar but distinct experiences, and the increase in new neurons promoted by NSI-189 could enhance this ability to make fine distinctions in memories. The hippocampus is also involved in spatial memory and navigation, enabling the formation of cognitive maps of the environment, with specialized cells called place cells encoding specific locations. Structural support of the hippocampus by NSI-189 could contribute to the optimal function of these spatial navigation systems. Additionally, although the consolidation of long-term memories eventually involves the transfer of information from the hippocampus to the cerebral cortex for permanent storage, the hippocampus remains involved in the retrieval of detailed autobiographical memories, and improved hippocampal function could facilitate access to these memories. Human studies have explored the effects of NSI-189 on neuropsychological batteries that assess different cognitive domains, including verbal memory, visual memory, attention, and executive functions, although the results should be interpreted considering the complexity of cognitive processes and individual variability in responses.

Modulation of emotional balance and resilience to stress

The hippocampus is not only crucial for cognition, but it also plays important roles in emotional regulation and stress responses. This brain region is densely populated with receptors for cortisol, the primary stress hormone, and functions as part of the negative feedback system that regulates the hypothalamic-pituitary-adrenal (HPA) axis, the system that coordinates physiological responses to stress. Under normal conditions, the hippocampus detects elevated cortisol levels and sends inhibitory signals to suppress further production of stress hormones. However, chronic stress can have deleterious effects on the hippocampus, including inhibition of neurogenesis, dendritic atrophy, and eventually a reduction in hippocampal volume, creating a vicious cycle where the damaged hippocampus is less effective at regulating the HPA axis, resulting in chronically elevated cortisol that continues to damage the hippocampus. NSI-189, by promoting hippocampal neurogenesis and supporting the structural restoration of the hippocampus, could help break this vicious cycle, potentially improving the hippocampus's ability to appropriately regulate stress responses. Research has explored whether restoring hippocampal structure with NSI-189 leads to improvements in mood regulation and resilience to stressful situations. The hippocampus is also connected to the amygdala, a region crucial for processing emotions, particularly fear, and to the prefrontal cortex, which is involved in the cognitive regulation of emotions. Improving hippocampal function could optimize these interactions, contributing to more balanced and adaptive emotional processing.

Optimization of functional connectivity between brain regions

The brain functions as a highly integrated network where different regions constantly communicate to coordinate complex cognitive and emotional processes. NSI-189 has been investigated for its ability to influence functional connectivity patterns between the hippocampus and other key brain regions. Connectivity between the hippocampus and the medial prefrontal cortex is particularly important for processes such as memory consolidation, where information temporarily stored in the hippocampus is gradually transferred to the cortex for long-term storage, and for the cognitive regulation of emotions, where the prefrontal cortex can modulate emotional responses by influencing the hippocampus and amygdala. By enhancing the structure and function of the hippocampus, NSI-189 could optimize these interactions, facilitating more efficient communication between regions. The connections between the hippocampus and the entorhinal cortex, which serves as the main gateway between the hippocampus and the rest of the cerebral cortex, are critical for the bidirectional flow of information, and structural support to the hippocampus could improve the efficiency of this communication. Studies using resting-state functional magnetic resonance imaging (fMRI), which measures temporal correlations in activity between different brain regions, have explored whether treatment with NSI-189 modifies these connectivity patterns. Optimizing functional connectivity could translate into better integration of information from different brain systems, potentially improving the ability to perform complex cognitive tasks that require the coordination of multiple mental processes, such as decision-making that involves integrating memories of past experiences, emotional evaluation of the current context, and planning for future actions.

Support for mitochondrial function and neuronal energy metabolism

Neurons have extraordinarily high energy demands due to the constant processes of maintaining ion gradients across their membranes, transmitting electrical signals, and synthesizing and transporting proteins and other cellular components. NSI-189 has been investigated for its ability to support mitochondrial function in neurons, mitochondria being the organelles responsible for generating most of the cell's ATP, its energy currency. Enhancing mitochondrial function is particularly important for metabolically demanding processes such as neurogenesis, where dividing and differentiating cells require large amounts of energy; dendritic growth, which requires extensive synthesis of membranes and cytoskeleton proteins; and synaptic transmission, which is continuously energy-intensive. NSI-189 can promote mitochondrial biogenesis, the formation of new mitochondria, thereby increasing the energy capacity of neurons. It can also improve the efficiency of oxidative phosphorylation, the process by which mitochondria generate ATP, ensuring that neurons can meet their energy demands without compromising other functions. Proper mitochondrial function is also important for intracellular calcium management, with mitochondria serving as calcium buffers that help regulate the concentrations of this important signaling ion. Additionally, mitochondrial health is linked to the production of reactive oxygen species, with dysfunctional mitochondria producing excessive amounts of these potentially damaging compounds. By supporting mitochondrial function, NSI-189 could contribute to maintaining appropriate redox balance in neurons, reducing oxidative stress that can damage cellular components.

Modulation of neuroinflammation and promotion of a neuroprotective environment

Neuroinflammation, the activation of inflammatory responses in the central nervous system, can have significant effects on brain function and processes such as neurogenesis. Microglial cells, the brain's resident immune cells, can exist in different activation states: in their basal surveillance state, microglia continuously scan the brain environment, detecting signs of damage or dysfunction. However, when they detect danger signals, they can activate into a pro-inflammatory state, secreting inflammatory cytokines such as TNF-alpha, IL-1beta, and IL-6, producing reactive oxygen species, and phagocytizing damaged material. While this inflammatory response is useful for eliminating pathogens and promoting repair in response to acute injuries, chronic microglial activation with sustained production of pro-inflammatory factors can be detrimental, inhibiting neurogenesis, damaging neurons, and compromising synaptic function. NSI-189 has been investigated for its ability to modulate microglial polarization, potentially favoring a more anti-inflammatory or reparative phenotype where microglia secrete anti-inflammatory cytokines such as IL-10 and neurotrophic factors that support neuronal health. This modulation of neuroinflammation could create a more favorable environment for NSI-189-stimulated neurogenesis, allowing newly born neurons to survive and mature appropriately. It could also protect existing neurons from chronic inflammatory damage. Reducing neuroinflammation could contribute to the beneficial effects of NSI-189 on cognitive function and emotional well-being, given that chronic brain inflammation is associated with various aspects of cognitive decline and mood disorders.

Support for gene expression related to neuronal plasticity and growth

NSI-189 has been investigated for its effects on gene expression patterns in the hippocampus, modulating the transcription of genes that encode proteins important for neuronal structure and function. Gene expression is the fundamental process by which the information encoded in DNA is converted into the proteins that carry out virtually all cellular functions. NSI-189 can influence the expression of genes related to the cytoskeleton, including those that encode tubulins and actins, which are the structural proteins that form the microtubules and actin filaments necessary for the growth of axons and dendrites, for the intracellular transport of components, and for the maintenance of neuronal shape. It can also modulate genes that encode synaptic proteins, including neurotransmitter receptors, postsynaptic scaffolding proteins that organize receptors in the postsynaptic density, and proteins involved in the release of synaptic vesicles—all critical for synaptic function. Genes encoding transcription factors, which are proteins that regulate the expression of other genes, are particularly interesting because their modulation can have cascading effects on multiple downstream genes. NSI-189 can also influence genes related to energy metabolism, the oxidative stress response, and cell signaling. This broad modulation of gene expression provides molecular mechanisms by which NSI-189 can orchestrate coordinated changes in multiple aspects of neuronal function, supporting not only individual processes such as dendritic growth, but also entire cellular programs such as neuronal differentiation during neurogenesis or the adaptive stress response.

Enhancement of neurotrophic signaling through increased TrkB receptors

Beyond increasing BDNF levels, NSI-189 has been investigated for its ability to enhance the expression of the TrkB receptor, the high-affinity receptor for BDNF. This dual potentiation, increasing both the ligand (BDNF) and its receptor (TrkB), could create a synergistic amplification of neurotrophic signaling. When BDNF binds to TrkB, it triggers receptor activation, which then initiates multiple intracellular signaling cascades, including MAP kinase pathways that promote growth and differentiation, the PI3K-AKT pathway that promotes cell survival, and the phospholipase C-gamma pathway that modulates synaptic function. By increasing TrkB expression in hippocampal neurons, NSI-189 could make these neurons more sensitive and responsive to available BDNF, whether endogenous BDNF produced by the brain itself or BDNF augmented by NSI-189. This increased sensitivity to neurotrophic signaling could translate into more pronounced effects on neuronal survival, neurite growth, synapse formation, and synaptic plasticity. The TrkB receptor responds not only to BDNF but also to neurotrophin-4, providing convergence points for multiple neurotrophic signals. Modulation of TrkB expression could also influence receptor trafficking to the plasma membrane, where it can interact with extracellular neurotrophins, and could affect receptor localization in different cellular compartments such as the soma, dendrites, or axon terminals, each with distinct functional implications.

The brain's secret garden where neurons can be reborn

Imagine your brain as a vast and complex city, with trillions of microscopic inhabitants called neurons constantly communicating with each other through electrical and chemical signals. For a long time, scientists thought this brain city was like an ancient city where all the buildings were already constructed at birth, and no new construction was possible during adulthood. But then they made a startling discovery: there is a secret garden in this city, hidden in a seahorse-shaped region called the hippocampus, where new neurons can be born even in adult brains. This special garden is called the dentate gyrus, and it's like a nursery where neural stem cells—baby cells that haven't yet decided what they want to be when they grow up—live, waiting for the right signals to divide and become fully functional neurons. This process of new neuron birth is called adult neurogenesis, and it's absolutely fascinating because it means your brain has a regenerative capacity no one imagined. However, this secret garden isn't always blooming vigorously. When you experience chronic stress, it's as if a frost has fallen on the garden, preventing fewer new neurons from blossoming. As you age, it's as if the garden soil becomes less fertile, and fewer new neurons are born each year. This is where NSI-189 comes in, acting like a specialized molecular gardener that arrives in this secret garden with specific tools designed to stimulate growth. Unlike other compounds that only protect existing plants from damage, NSI-189 actually gets seeds to germinate and new plants to grow.

The molecular architect who redesigns the neural landscape

But NSI-189 isn't just a gardener planting seeds; it's also an architect redesigning the entire structure of the neural landscape. Think of each neuron as a tree with roots and branches. The roots represent the axon, the long cable that carries electrical signals from the neuron's cell body to other neurons, and the branches represent the dendrites, the branching structures that receive signals from other neurons. Now imagine that each point where one branch of a tree touches the branch of another tree is a communication site called a synapse, where the trees can pass chemical messages to each other. The more branches each tree has, and the more densely branched those branches are, the more points of contact and communication are possible. NSI-189 acts as an architect that not only plants new trees through neurogenesis but also stimulates existing trees and newly planted trees to extend their branches much more profusely. This dendritic branching process is as if each neuron decides to become a more leafy and complex tree, with branches extending in more directions and subdividing into smaller branches, creating an intricate three-dimensional network. But there's more: on each dendritic branch grow tiny protrusions called dendritic spines, which are like small bulbs where most excitatory synapses form. NSI-189 also promotes the formation of these dendritic spines, as if it were adding more fruit to each branch of the tree. The result of all this architectural remodeling is that the hippocampus, this special garden in your brain, literally expands in volume, not only because there are more new neuronal trees, but because each tree has become larger, more branched, and more connected to its neighbors.

The molecular fertilizer that nourishes brain growth

Now, for all this growth and remodeling to occur, neurons need molecular nutrition—something to feed and support them as they grow. This is where an extraordinary protein called BDNF comes in. BDNF stands for brain-derived neurotrophic factor, but it's best thought of as the most important molecular fertilizer for neurons. BDNF is like a chemical messenger that travels between neurons carrying a message that says, "Grow, thrive, form new connections, and don't give up." When a BDNF molecule encounters a neuron that has special receptors called TrkB on its surface, it's like a key fitting into a lock, opening a door that triggers a cascade of events within the neuron. This cascade is like a chain reaction where one signal activates the next, which activates the next, resulting in profound changes in the neuron's behavior: proteins that protect the neuron from dying are activated, the DNA in the nucleus begins to read genes that encode proteins necessary for growth, the cytoskeleton—the neuron's internal skeleton—reorganizes, allowing neurites to grow, and new synaptic proteins are synthesized and transported to the synapses. What's fascinating about NSI-189 is that it has a dual effect on this system: first, it increases the amount of BDNF that neurons produce and secrete, as if it were increasing fertilizer production in the brain's local factory. Second, it increases the number of TrkB receptors on the surface of neurons, as if it were installing more locks that can respond to the BDNF fertilizer. This dual strategy is brilliant because it is amplifying the signal at both ends: there is more messenger (BDNF) and more receptors to receive the message (TrkB), resulting in enhanced neurotrophic signaling that vigorously nourishes neuronal growth.

Power plants that drive neural development

This entire process of building new neurons, extending branched dendrites, and forming synapses is extraordinarily energy-intensive. Think of mitochondria as tiny power plants within each neuron; there are typically hundreds or thousands of them distributed throughout the cell, especially concentrated in areas where energy demand is highest, such as synaptic terminals where neurotransmitters must be constantly synthesized and released. These mitochondrial power plants take the fuel you get from your food, particularly glucose and oxygen, and process it through a series of elegant chemical reactions called oxidative phosphorylation, generating ATP molecules that are like charged molecular batteries that can be used to power virtually everything the neuron needs to do. Maintaining the sodium and potassium ion gradients across the neuronal membrane, which are necessary for generating electrical signals, consumes approximately half of all the energy a neuron uses. Transporting proteins and other materials from the cell body to distant axon terminals consumes energy, synthesizing neurotransmitters consumes energy, and certainly building new cellular structures during neuronal growth consumes massive amounts of energy. NSI-189 has been investigated for its effects on mitochondrial function, and it appears to improve how efficiently these powerhouses generate ATP. It's as if NSI-189 were an engineer optimizing the powerhouses, making them run more smoothly and produce more electricity with the same fuel. It can promote mitochondrial biogenesis, which is the process of building new powerhouses, increasing the neuron's overall energy capacity. It can also reduce the production of reactive oxygen species, which are like dangerous sparks jumping from the powerhouses and can damage cellular components if produced in excess. By improving mitochondrial function, NSI-189 ensures that neurons have the energy needed to maintain all the growth and remodeling processes it is stimulating.

The security guards who maintain peace in the neural neighborhood

In the city of the brain, it's not all neurons. There's another type of inhabitant called microglia, which are like the brain's security guards or police. These cells are constantly patrolling, extending and retracting their arms to scan the local environment for signs of trouble, such as damaged neurons, misfolded proteins, or invaders like bacteria or viruses. When microglia detect a problem, they can activate into a state of high alert, where they begin secreting inflammatory signaling molecules like cytokines. These are like alarm sirens that alert other cells to the problem, and they can also phagocytize, or "eat," debris and damaged material, cleaning up the neighborhood. In acute situations like an infection or injury, this inflammatory response from microglia is absolutely necessary and beneficial, helping to eliminate the threat and initiate repair processes. The problem arises when microglia become chronically stuck in this inflammatory, high-alert state, like security guards who are constantly on edge, seeing threats where none exist, and continuously setting off their sirens. This chronic neuroinflammation is like living in a neighborhood where sirens blare constantly, creating a stressful environment that isn't conducive to growth. The pro-inflammatory cytokines secreted by activated microglia can inhibit neurogenesis, resulting in fewer new neurons being born in our secret garden of the dentate gyrus. They can also damage existing neurons and compromise synaptic connections. NSI-189 appears to be able to modulate the behavior of microglia, like a diplomatic mediator convincing overactive security guards to calm down and adopt a more balanced approach. It can promote what scientists call polarization toward an anti-inflammatory or reparative phenotype, where microglia reduce their production of inflammatory cytokines and instead secrete factors that support neuronal health and tissue repair. This modulation of inflammation creates a much more favorable environment for the neurogenesis that NSI-189 is trying to promote.

The genetic switches that orchestrate the symphony of growth

Within the nucleus of each neuron, neatly coiled like a vast library, lies the DNA that contains the instructions for making all the proteins the cell needs. But DNA isn't simply read from beginning to end continuously; rather, different genes are switched on or off at specific times depending on the signals the cell receives. Think of DNA as a giant musical score for an orchestra, and transcription factors as conductors who decide which sections of the orchestra should play at any given moment—whether the violins should play loudly or softly, whether the trumpets should join in or remain silent. NSI-189 influences which genes are activated in the neurons of the hippocampus, modulating the expression of genes that encode structural proteins needed to build the cytoskeleton, synaptic proteins needed for communication between neurons, metabolic enzymes needed to produce energy, and transcription factors that are like orchestra conductors, in turn controlling other genes. It is particularly interesting that NSI-189 can activate genes related to neuronal plasticity, the brain's ability to change and adapt, and genes related to the response to neurotrophic factors, creating a situation where neurons are better prepared to respond to growth signals. It can also modulate genes related to the cytoskeleton, particularly those that encode tubulins and actins, which form the tracks and cables along which dendrites and axons can extend. By conducting this genetic orchestra, NSI-189 coordinates a coherent program of cellular changes that result in neurons that are in a mode of growth and construction rather than mere maintenance. It is as if the compound is changing the music the cell is playing, from a tranquil piece of maintenance to a vibrant symphony of growth and renewal.

The communication bridges that connect distant brain islands

The hippocampus, our secret garden where NSI-189 primarily works, is not an isolated island in the brain. It is extensively connected to many other brain regions by communication cables that are bundles of axons called white matter tracts. Imagine the brain as an archipelago of islands, where each island is a different brain region with specialized functions, and the bridges between islands are these connections that allow regions to communicate and coordinate their activities. The hippocampus has particularly important bridges with the prefrontal cortex, which is like the brain's CEO involved in planning, decision-making, and impulse control. It has connections with the amygdala, which is like the brain's alarm system that detects threats and coordinates emotional responses, particularly fear. It has extensive connections with multiple areas of sensory cortex that process information from your senses. And it has critical connections with the entorhinal cortex, which serves as the main train station where information enters and leaves the hippocampus. What's fascinating is that when NSI-189 improves the structure of the hippocampus through neurogenesis and dendritic remodeling, it can change how the hippocampus communicates with other brain regions. It's like renovating and expanding a major train station, which alters traffic patterns across the entire transportation network. Studies using neuroimaging techniques have investigated what they call functional connectivity, which is essentially how synchronized the activities of different brain regions are, as if they were having a coordinated conversation. When the hippocampus functions better structurally, it can participate more effectively in these conversations with other regions, potentially enhancing complex functions that require coordination among multiple brain areas, such as forming memories that integrate emotional, sensory, and contextual information, or regulating emotional states through interaction between the hippocampus and the prefrontal cortex, which can exert cognitive control over emotional responses.

The full story: a brain city renovator

If we had to summarize how NSI-189 works in one grand, unifying metaphor, it would be like an extraordinarily talented urban renovator arriving in a specific neighborhood of the brain's city—the hippocampus—with a comprehensive revitalization plan. First, it identifies the special nursery in the dentate gyrus where neural stem cells reside, awaiting signals to divide, and actively stimulates these cells to awaken and begin creating new baby neurons, much like activating a construction factory that had been operating at half capacity. Second, it not only creates new neurons but also acts as a landscape architect, stimulating both the new and existing neurons to extend their dendritic branches more profusely, creating a denser and richer canopy in the neuronal forest, and to cultivate more dendritic spines, which are the sites where communication between neurons occurs. Third, it dramatically increases the production of the molecular fertilizer BDNF while simultaneously installing more TrkB receptors on neurons, creating an amplified nutrition system where there is more fertilizer available and more receptors to capture it, vigorously fueling all growth. Fourth, it enhances the mitochondrial powerhouses in each neuron, ensuring there is enough energy to drive all these metabolically costly processes of building and remodeling. Fifth, it calms the microglial security guards that might be in a state of chronic alert, reducing inflammation that could interfere with growth and creating a more peaceful and conducive environment for neuronal flourishing. Sixth, it enters the nucleus of neurons and adjusts which genes are being read and transcribed, conducting a genetic orchestra that plays a symphony of growth, plasticity, and renewal. And seventh, as the hippocampus strengthens structurally and functionally through all these processes, it improves how this crucial region communicates with other parts of the brain through connectivity networks, optimizing complex functions that depend on coordination among multiple brain regions. The end result of this entire renewal effort is an expanded hippocampus, with more neurons, more richly branched and connected neurons, more robust neurotrophic signaling, more efficient energy metabolism, less chronic inflammation, and better integration into broader brain networks. This revitalized hippocampus is better equipped to perform its critical functions in forming new memories, processing spatial information, contributing to emotional regulation, and participating in appropriate stress responses. NSI-189 does not force the brain to do anything unnatural; rather, it awakens and amplifies regenerative capacities that the brain already possesses but that may be dormant or suppressed by stress, aging, or other factors.

Stimulation of proliferation of neural progenitor cells in the subgranular zone of the dentate gyrus

NSI-189 exerts neurogenic effects by modulating the proliferation of neural progenitor cells residing in the subgranular zone of the dentate gyrus of the hippocampus, one of the major neurogenic niches in the adult mammalian brain. The subgranular zone contains a population of progenitor cells with characteristics of radial glial cells, classified as type 1 cells or neural stem cells, which have self-renewal capacity and can generate transient amplification progenitor cells classified as type 2 cells. These progenitor cells proliferate more rapidly and subsequently differentiate into type 3 neuroblasts, which eventually mature into granule neurons. NSI-189 has been investigated for its effects on each stage of this neurogenic lineage. In vivo studies using cell labeling of dividing cells by administering nucleotide analogs such as bromodeoxyuridine (BrdU) or iododeoxyuridine (IdU), which are incorporated into DNA during the S phase of the cell cycle, followed by immunohistochemical analysis at later time points, have demonstrated that treatment with NSI-189 increases the number of BrdU-positive cells in the subgranular zone, indicating increased cell proliferation. Co-labeling with stage-specific markers such as Sox2, which labels progenitor cells, DCX (doublecortin), which labels immature neuroblasts, and NeuN, which labels mature neurons, has allowed for the characterization of the neurogenic lineage stages at which NSI-189 has the most pronounced effects. The molecular mechanisms by which NSI-189 stimulates progenitor proliferation include activation of intracellular signaling pathways that regulate cell cycle progression, modulation of transcription factor expression that controls progenitor cell identity and proliferation capacity, and effects on the neurogenic niche microenvironment, including interactions with vasculature and astrocytes that provide support and regulatory signals. Signaling pathways that have been implicated include the ERK (extracellular signal-regulated kinase) pathway, a component of the MAP kinase cascade that promotes cell cycle progression by phosphorylating cycle regulators such as cyclins; the PI3K-AKT pathway, which promotes cell survival and proliferation through effects on multiple downstream substrates; and potentially the Wnt pathway, which is critical for stem cell maintenance and neurogenesis promotion. The regional specificity of neurogenic effects of NSI-189 to the hippocampus, particularly the dentate gyrus, rather than to other brain regions suggests that molecular targets of NSI-189 are preferentially expressed in this neurogenic niche, or that unique features of the hippocampal microenvironment make progenitor cells there particularly responsive to NSI-189.

Promotion of neuronal survival and differentiation of newborn cells

Beyond stimulating initial progenitor cell proliferation, NSI-189 has been investigated for its effects on the survival of newborn cells during the critical post-mitotic period when a large proportion of new neurons normally die by apoptosis. Studies using a pulse-chasing labeling paradigm, where BrdU is administered to label a cohort of dividing cells at a specific time point, followed by analyses at subsequent time points weeks later, have shown that NSI-189 treatment increases not only the number of initially labeled cells but also the fraction of labeled cells that survive in subsequent weeks. This suggests that NSI-189 promotes the survival of immature neurons in addition to progenitor cell proliferation. The mechanisms of neuronal survival involve multiple anti-apoptotic pathways that are modulated by neurotrophic factors, neuronal activity, and appropriate synaptic integration. NSI-189 can influence survival by increasing the expression and secretion of neurotrophic factors, particularly BDNF, which activates the TrkB signaling pathway, leading to AKT phosphorylation. AKT phosphorylates and inactivates pro-apoptotic BCL-2 family proteins such as BAD and activates transcription factors like CREB, which promote the expression of survival genes. NSI-189 can also promote neuronal differentiation from progenitors to a mature neuronal phenotype by modulating pro-neuronal transcription factors such as NeuroD1, which is critical for the differentiation of granule neurons in the dentate gyrus. Proper differentiation includes the development of characteristic neuronal morphology with a single neurite extension that becomes an axon projecting toward CA3, and multiple neurites that become dendrites extending into the molecular layer where they receive inputs from the entorhinal cortex. NSI-189 may support these morphogenetic processes by affecting cytoskeleton dynamics, particularly by reorganizing actin filaments and microtubules that drive neurite extension, and by regulating axonal guidance proteins that direct growing axons to their appropriate targets.

Upregulation of BDNF expression and modulation of neurotrophic signaling

Brain-derived neurotrophic factor (BDNF) is a neurotrophin that plays critical roles in neuronal survival, differentiation, neurite growth, synaptic formation, and synaptic plasticity by binding to the high-affinity receptor TrkB, a tyrosine kinase receptor. NSI-189 has been extensively investigated for its effects on BDNF expression in the hippocampus, with multiple studies reporting increased levels of BDNF messenger RNA and BDNF protein in hippocampal tissue after treatment. The mammalian BDNF gene has a complex structure with multiple alternative promoters that generate multiple mRNA transcripts that differ in their 5' untranslated regions but all encode the same mature BDNF protein. BDNF expression can be regulated at the transcriptional level by transcription factors that bind to promoter regions, with CREB (cAMP response element-binding protein) being particularly important since BDNF promoter IV contains multiple CREB binding sites. NSI-189 can increase CREB activity by activating upstream kinases that phosphorylate CREB at serine-133, a post-translational modification that enhances CREB's transcriptional activity. Kinases that can phosphorylate CREB include PKA (protein kinase A), which is activated by cAMP; CaMKII (calmodulin-dependent kinase II), which is activated by increased intracellular calcium; and MAP kinase family kinases such as ERK and p38. Synthesized BDNF is secreted from neurons in an activity-dependent manner, with BDNF being stored in dense secretory vesicles that are released in response to neuronal depolarization and calcium influx. Once secreted, BDNF binds to TrkB receptors on neighboring neurons or on the same neuron in an autocrine manner, initiating signaling cascades that include the RAS-ERK pathway, which promotes growth and differentiation by phosphorylating transcription factors such as Elk-1 and CREB; the PI3K-AKT pathway, which promotes survival by inactivating pro-apoptotic proteins and activating mTOR, which promotes protein synthesis; and the PLCγ (phospholipase C gamma) pathway, which generates second messengers IP3 and DAG that modulate intracellular calcium and activate PKC, respectively. The increase in BDNF induced by NSI-189 may have particular effects on neurogenesis, given that BDNF is necessary for the survival of newly born neurons; it may have effects on synaptic plasticity, given that BDNF modulates synaptic transmission efficiency and is necessary for long-term potentiation; and it may have neuroprotective effects by promoting the survival of existing neurons under stress conditions.

Increased expression of TrkB receptor and potentiation of neurotrophic signaling

Complementing its effects on BDNF expression, NSI-189 has been investigated for its effects on TrkB receptor expression, creating synergistic amplification of neurotrophic signaling where both ligand and receptor are increased. The TrkB receptor exists in multiple isoforms generated by alternative splicing, with TrkB-FL (full length) being the catalytically active isoform containing an intracellular tyrosine kinase domain, and TrkB-T1 and TrkB-T2 being truncated isoforms lacking the kinase domain, which can function as dominant-negative receptors or have alternative signaling roles. NSI-189 can modulate TrkB-FL expression in particular, increasing mRNA and protein levels detectable by qPCR and Western blot, respectively. The transcriptional regulation of TrkB involves multiple transcription factors that bind to promoter regions of the NTRK2 gene, which encodes TrkB. These factors include factors such as CREB, Fos-Jun family transcription factors that form the AP-1 complex, and potentially neuronal lineage-specific factors. Increased TrkB expression results in a higher density of receptors in the neuronal plasma membrane, enhancing the ability of neurons to respond to available BDNF. The trafficking of TrkB receptors to the plasma membrane is regulated by vesicular transport along microtubules, with receptors being inserted into the membrane, particularly in postsynaptic regions where they can respond to BDNF released from presynaptic terminals. NSI-189 can also modulate the subcellular localization of TrkB, with some studies suggesting effects on receptor trafficking to dendrites and dendritic spines, where they can more effectively participate in the regulation of synaptic plasticity. Activation of TrkB by BDNF induces receptor dimerization and autophosphorylation of tyrosine residues in the intracellular domain, creating docking sites for adaptor proteins that initiate signaling cascades. Specific tyrosine residues that are phosphorylated recruit specific proteins: Y515 recruits Shc, which activates the RAS-ERK pathway; Y816 recruits PLCγ; and other residues recruit proteins that activate the PI3K-AKT pathway. Enhancement of TrkB signaling by NSI-189 through dual enhancement of BDNF and TrkB can result in more robust and sustained activation of downstream pathways, with amplified effects on neuronal survival, neurite growth, and synaptic plasticity compared to modulation of BDNF or TrkB alone.

Promotion of dendritic arborization and dendritic spine formation

NSI-189 has been investigated for its effects on the dendritic morphology of hippocampal neurons, promoting dendritic extension and branching, and the formation of dendritic spines, which are primary sites of excitatory synapses. Morphological analysis using techniques such as Golgi staining, which impregnates a random subpopulation of neurons allowing visualization of complete morphology, or intracellular filling with fluorescent tracers followed by confocal or two-photon microscopy, has shown that treatment with NSI-189 increases total dendritic length, the number of dendritic branches (quantified by Sholl analysis, which measures the number of dendritic intersections with concentric circles at incremental distances from the soma), and dendritic tree complexity. The molecular mechanisms that regulate dendritic growth involve dynamic cytoskeleton reorganization, particularly actin polymerization at the tips of growing dendrites, which drives extension, and microtubule stabilization by microtubule-associated proteins (MAPs) such as MAP2, which is highly expressed in dendrites. NSI-189 can modulate the expression of cytoskeletal proteins and regulators of cytoskeleton dynamics, including Rho GTPases (RhoA, Rac1, Cdc42), which are molecular switches that, when in their active GTP-bound form, regulate actin reorganization: Rac1 and Cdc42 generally promote protrusion and branching, while RhoA can promote retraction. BDNF-TrkB signaling, which is upregulated by NSI-189, activates pathways that modulate Rho GTPases, favoring dendritic growth. Dendritic spines are small protrusions that emerge from dendritic shafts and contain postsynaptic apparatus, including glutamate receptors, scaffolding proteins, and signaling machinery. Dendritic spine density, which is the number of spines per unit of dendritic length, can be increased by NSI-189, thereby increasing the total number of excitatory synapses a neuron can form. Spine morphology is also functional, with spines classified as thin filipodia, which are transient and may represent developing spines; thin spines with a narrow neck and bulbous head, which are abundant and plastic; mushroom-shaped spines with a wider neck and large head, which represent mature and stable spines; and short, thick, stubby spines. NSI-189 can promote the formation of new spines and can modulate the maturation of immature spines toward more mature morphologies. Spinogenesis mechanisms involve local actin nucleation at spine formation sites by nucleating complexes such as Arp2/3, protrusion extension by actin polymerization, and spine stabilization by recruitment of postsynaptic proteins such as PSD-95, which is a scaffolding protein that organizes glutamate receptors.

Modulation of glutamate receptors and enhancement of synaptic plasticity

Glutamate is the primary excitatory neurotransmitter in the mammalian brain, and glutamate receptors, particularly NMDA and AMPA receptors, are critical for synaptic transmission and synaptic plasticity in the hippocampus. NSI-189 has been investigated for its effects on the expression and function of these receptors. NMDA receptors are ligand- and voltage-gated ion channels that require the binding of glutamate and the co-agonist glycine or D-serine. They require depolarization of the postsynaptic membrane to remove magnesium blockage from the channel pore, allowing calcium influx into the postsynaptic dendritic spine. This calcium triggers signaling cascades that induce long-term potentiation (LTP), which is a lasting strengthening of synaptic efficiency. NMDA receptors are heterotetramers typically composed of two GluN1 subunits and two GluN2 subunits (GluN2A, GluN2B, GluN2C, or GluN2D), with subunit composition determining biophysical and pharmacological properties. NSI-189 can modulate the expression of NMDA receptor subunits, particularly GluN2A and GluN2B, which are predominant in the hippocampus, with some studies reporting increased protein levels. AMPA receptors mediate most fast excitatory synaptic transmission and are also heterotetramers composed of GluA1, GluA2, GluA3, and GluA4 subunits. The insertion of additional AMPA receptors into the postsynaptic membrane during long-term transmission (LTP) is a key mechanism of synaptic strengthening. NSI-189 can facilitate AMPA receptor trafficking to synapses, a process regulated by phosphorylation of AMPA subunits by kinases such as CaMKII and PKA, and by scaffolding proteins that anchor receptors in postsynaptic density. The increased expression of glutamate receptors combined with effects on receptor trafficking can result in a higher density of functional receptors at synapses, increasing the magnitude of excitatory postsynaptic currents and facilitating the induction and expression of long-term post-synaptic potentials (LTPs). Electrophysiological studies using patch-clamp recording of hippocampal slices have investigated whether NSI-189 treatment modulates the amplitude of excitatory postsynaptic potentials (EPSPs), facilitates LTP induction via high-frequency stimulation protocols, or affects other forms of plasticity such as long-term depression (LTD). The effects on glutamate receptors and synaptic plasticity may contribute to the effects of NSI-189 on cognitive function, given that LTP in the hippocampus is considered a cellular mechanism underlying the formation of spatial and episodic memories.

Activation of intracellular signaling pathways ERK, AKT and mTOR

Although the direct molecular targets of NSI-189 are not fully characterized, studies have investigated its effects on intracellular signaling pathways known to regulate neuronal growth, survival, and differentiation. The ERK (extracellular signal-regulated kinase) pathway is a component of the MAP kinase (mitogen-activated protein kinase) cascade, which transduces signals from cell-surface receptors to the nucleus. Typical activation involves receptor-activated small G protein RAS via guanine nucleotide exchange factors (GEFs). RAS-GTP activates RAF, a MAP kinase kinase (MAPKKK) family kinase. RAF phosphorylates and activates MEK, a MAP kinase kinase (MAPKKK), and MEK phosphorylates and activates ERK, a MAP kinase (MAPK). Activated ERK translocates to the nucleus where it phosphorylates transcription factors such as Elk-1, CREB, and c-Fos, promoting the expression of early response genes and genes that regulate proliferation and differentiation. NSI-189 has shown in in vitro studies the ability to increase ERK phosphorylation in cultured neurons, indicating activation of this pathway. The PI3K-AKT pathway is activated by tyrosine kinase receptors, including TrkB, or by G protein-coupled receptors, leading to the activation of PI3K (phosphatidylinositol-3-kinase), which phosphorylates PIP2, generating PIP3. PIP3 recruits AKT (also known as PKB) to the membrane where it is phosphorylated and activated by PDK1 and mTORC2. Activated AKT phosphorylates multiple substrates that promote cell survival, including BAD, a pro-apoptotic protein that, when phosphorylated by AKT, is sequestered by 14-3-3 proteins and cannot promote apoptosis; MDM2, which, when phosphorylated by AKT, inactivates p53, reducing pro-apoptotic signaling; and FOXO, transcription factors that, when phosphorylated by AKT, are excluded from the nucleus, preventing the transcription of pro-apoptotic genes. AKT also activates mTORC1 (mammalian target of rapamycin complex 1) by phosphorylating and inactivating TSC2, an mTORC1 inhibitor. mTORC1 is a central kinase that regulates protein synthesis by phosphorylating S6K and 4E-BP1, which regulate mRNA translation, ribosome biogenesis, metabolism, and inhibits autophagy. mTORC1 activation is necessary for cell growth, including neuronal cell body growth and neurite extension. NSI-189 has been shown to increase phosphorylation of AKT and downstream components of the mTOR pathway in neurons, suggesting activation of this pathway. The convergence of activation of multiple signaling pathways by NSI-189 may result in synergistic effects on processes such as neurogenesis, where progenitor proliferation is promoted by ERK, survival of new neurons is promoted by AKT, and growth and differentiation are supported by mTOR.

Improved mitochondrial function and neuronal energy metabolism

Neurons have extraordinary energy demands due to processes such as maintaining membrane potentials through active ion pumping, synaptic transmission requiring neurotransmitter synthesis and release, and axonal transport moving materials from the soma to distant terminals. Mitochondria generate most cellular ATP through oxidative phosphorylation, where the electron transport chain in the inner mitochondrial membrane pumps protons from the matrix into the intermembrane space, creating an electrochemical gradient that drives ATP synthase. NSI-189 has been investigated for its effects on mitochondrial function in neurons by measuring parameters such as oxygen consumption, reflecting respiratory chain activity, measured by high-resolution respirometry or oxygen-selective electrodes; ATP production, quantified by luciferase-based bioluminescence assays; mitochondrial membrane potential, measured using voltage-sensitive fluorescent dyes such as TMRM or JC-1; and reactive oxygen species (ROS) production, measured by fluorescent probes such as MitoSOX or DCF. Some studies have reported that NSI-189 can improve mitochondrial respiratory capacity by increasing peak oxygen uptake, enhance respiratory coupling (the efficiency of converting oxygen consumption into ATP synthesis), and reduce the production of mitochondrial reactive oxygen species (ROS), which can damage cellular components. The mechanisms by which NSI-189 may improve mitochondrial function include promoting mitochondrial biogenesis by activating PGC-1α (peroxisome proliferator-activated receptor coactivator 1α), a master regulator that coordinates the expression of nuclear and mitochondrial genes necessary for the formation of new mitochondria; enhancing the function of respiratory chain complexes by affecting the expression or assembly of subunits; and reducing mitochondrial oxidative stress by upregulating mitochondrial antioxidant enzymes such as superoxide dismutase 2 (SOD2 or MnSOD), which converts superoxide to hydrogen peroxide that is subsequently detoxified by catalase or glutathione peroxidase. The enhancement of mitochondrial energy metabolism by NSI-189 is particularly relevant for metabolically costly processes such as neurogenesis where dividing and differentiating cells have high energy demands, dendritic growth which requires extensive synthesis of membranes and proteins, and synaptic plasticity where remodeling of dendritic spines and synthesis of synaptic components require ATP.

Modulation of microglial activation and reduction of neuroinflammation

Microglia are resident immune cells of the central nervous system derived from myeloid lineage, constituting approximately 10–15% of cells in the brain. In a basal surveillance state, microglia have a branched morphology with dynamically extending cellular processes that scan the brain parenchyma, detecting damage signals via receptors for damage-associated molecular patterns (DAMPs) and pathogen-associated molecular patterns (PAMPs). When microglia detect activation signals, they can transform into an activated phenotype characterized by process retraction, soma enlargement, and the production of inflammatory mediators. Microglial activation can be classified spectrally, ranging from a pro-inflammatory phenotype (classically termed M1), characterized by the production of pro-inflammatory cytokines such as TNF-alpha, IL-1beta, and IL-6, the production of reactive oxygen and nitrogen species via NADPH oxidase and inducible nitric oxide synthase (iNOS), and increased phagocytic capacity, to an anti-inflammatory or reparative phenotype (classically termed M2), characterized by the production of anti-inflammatory cytokines such as IL-10 and TGF-beta, the production of neurotrophic factors, and participation in the resolution of inflammation and tissue repair. Chronic microglial activation toward a pro-inflammatory phenotype can have deleterious effects on brain function, including inhibition of neurogenesis through the effects of pro-inflammatory cytokines on progenitor cells, damage to neurons through the production of toxic mediators, and impairment of synaptic function. NSI-189 has been investigated for its effects on microglial activation and polarization using techniques such as immunohistochemistry for microglial activation markers, including Iba1, which labels all microglia and whose intensity increases with activation; CD68, which labels phagocytic microglia; and iNOS, which labels pro-inflammatory microglia. Cytokine levels have also been measured in brain tissue or culture medium using ELISA or cytokine arrays, and gene expression analysis in isolated microglia using FACS followed by qPCR or RNA sequencing. Some studies have reported that NSI-189 treatment reduces pro-inflammatory microglial activation markers, lowers pro-inflammatory cytokine levels, and increases markers of anti-inflammatory or reparative phenotypes. The mechanisms by which NSI-189 could modulate microglia include direct effects on microglia if the compound penetrates these cells, indirect effects mediated by factors secreted from neurons treated with NSI-189 such as neurotrophins that can have anti-inflammatory effects on microglia, and reduction of activation signals by improving neuronal health by reducing the release of DAMPs from stressed neurons.

Regulation of gene expression through modulation of transcription factors

NSI-189 has been investigated for its effects on gene expression profiles in the hippocampus using functional genomics techniques such as DNA microarrays or RNA sequencing (RNA-seq), which allow for the simultaneous quantification of mRNA levels in thousands of genes. These studies have identified sets of genes whose expression is modulated by NSI-189 treatment, providing insights into the underlying molecular mechanisms. Upregulated genes include those related to neurotrophic factors such as BDNF, as discussed; cytoskeleton-related genes, including tubulins (TUBA, TUBB), which are microtubule subunits necessary for neuronal structure and intracellular transport; actins (ACTB, ACTG1), which form filaments necessary for cell morphology and motility; and microtubule-associated proteins such as MAP2, which is highly expressed in dendrites and stabilizes microtubules; genes related to synaptic function, including glutamate receptor subunits (GRIN1, GRIN2A, GRIN2B, which encode NMDA receptor subunits; GRIA1, GRIA2, which encode AMPA receptor subunits); postsynaptic scaffolding proteins such as PSD-95 (DLG4), which organizes receptor complexes in postsynaptic density; and synapsins, which regulate neurotransmitter release; and genes related to energy metabolism, including glycolysis and cyclosporine enzymes. Krebs cycle genes, subunits of mitochondrial respiratory chain complexes, and regulators of mitochondrial biogenesis, as well as genes related to the oxidative stress response, including antioxidant enzymes such as superoxide dismutases (SOD1, SOD2), catalase, and glutathione peroxidases, are affected. Downregulated genes may include those related to apoptosis, inflammation, or neuronal growth inhibitors. Gene expression regulation by NSI-189 occurs through modulation of the activity of transcription factors, which are proteins that bind to specific DNA sequences in promoter or enhancer regions of target genes, regulating their transcription. Transcription factors implicated in the effects of NSI-189 include CREB, which is activated by phosphorylation at serine-133 by kinases such as PKA, CaMKII, or ERK, and then binds to cAMP response elements (CREs) in the promoters of target genes, promoting their transcription; Fos-Jun family factors that form the AP-1 complex and are induced as immediate early response genes in response to stimulation; and neuronal lineage-specific transcription factors such as NeuroD1, which promotes neuronal differentiation. NSI-189 can increase the activity of these transcription factors by activating signaling pathways that lead to their phosphorylation, by increasing their expression, or by modulating transcriptional co-activators or co-repressors that regulate their activity.

Modulation of hippocampal functional connectivity through structural effects

The hippocampus is extensively connected to multiple brain regions via white matter tracts, which are bundles of myelinated axons, forming neural circuits that mediate complex cognitive and emotional functions. Key connections include a trisynaptic circuit within the hippocampus, where information flows from the entorhinal cortex via the perforant pathway to the dentate gyrus, then from the dentate gyrus via mossy fibers to the CA3 region, then from CA3 via Schaffer collaterals to the CA1 region, and finally from CA1 back to the entorhinal cortex and also to the subiculum; connections with the medial prefrontal cortex, particularly the prelimbic and infralimbic cortex, which are involved in memory consolidation, fear extinction, and cognitive regulation of emotion; bidirectional connections with the amygdala, which is involved in emotional processing and modulation of memory consolidation based on the emotional valence of experiences; and connections with the hypothalamus, particularly nuclei that regulate the hypothalamic-pituitary-adrenal (HPA) axis, which coordinates stress responses. Functional connectivity between these regions can be assessed using resting-state functional magnetic resonance imaging (rs-fMRI), which measures temporal correlations in BOLD signals between distinct brain regions, reflecting synchronization of activity that suggests functional communication, or using effective connectivity, which models directional causal influences between regions. NSI-189, through structural enhancement of the hippocampus—including increased volume, increased neuronal number via neurogenesis, and enhanced local connectivity through increased dendritic spines and synapses—can modulate how the hippocampus functionally interacts with these connected regions. Neuroimaging studies have investigated whether NSI-189 treatment results in changes in patterns of functional connectivity, with some studies reporting changes in connectivity between the hippocampus and medial prefrontal cortex, or between the hippocampus and other default mode network regions that are active during rest and involved in internally directed processes such as reminiscence, future planning, and theory of mind. The mechanisms by which local structural changes in the hippocampus can translate into changes in functional connectivity at the network level include effects on information processing efficiency in the hippocampus that can alter the timing and content of outputs to connected regions, changes in excitation-inhibition balance in the hippocampus that can modulate neuronal oscillations that coordinate activity between regions, and potentially effects on the plasticity of long-range connections if new neurons form projections to distant regions or if expanded dendrites receive more inputs from distant regions.

Potential modulation of neuronal oscillations and temporal coordination of activity

Neuronal oscillations are rhythmic patterns of electrical activity in the brain that emerge from synchronized activity of neuronal populations, measured by electroencephalography (EEG) or local field potential (LFP) recordings with implanted electrodes. Different oscillation frequency bands are associated with different brain states and cognitive functions: theta oscillations (4–8 Hz) in the hippocampus are involved in spatial navigation, encoding episodic memories, and coordination of activity between the hippocampus and cortex; gamma oscillations (30–100 Hz) are involved in sensory processing, attention, and memory consolidation; and sharp-wave ripple oscillations (120–250 Hz) occur during slow-wave sleep and periods of wakeful quiet and are involved in replaying sequences of neuronal activity that mediate memory consolidation by transferring information from the hippocampus to the cortex. NSI-189, through its effects on hippocampal structure and function, could modulate these oscillations. The mechanisms that generate oscillations involve interactions between excitatory neurons and inhibitory interneurons, particularly parvalbumin-expressing interneurons that innervate perisomatic regions of excitatory neurons and can fire at very high frequencies, synchronizing populations of excitatory neurons. NSI-189, through its effects on neurogenesis, could modulate oscillations, given that young granule neurons have distinct electrophysiological properties from mature neurons, including greater excitability and a lower threshold for LTP induction, and its incorporation into circuits can alter network dynamics. Effects on the expression and function of glutamate and GABA receptors, on dendritic morphology (which affects synaptic integration properties), and on interregional connectivity could also influence oscillations. In vivo electrophysiological studies using LTP recording in NSI-189-treated animals could investigate changes in the spectral power of different frequency bands, changes in coherence (which measures synchronization between regions), or changes in phase-amplitude coupling (where the phase of low-frequency oscillation modulates the amplitude of high-frequency oscillation).