Research goal
Covers compounds researched for cognitive function, memory, focus, anxiety modulation, and neuroprotective effects in preclinical and clinical settings.
| Compound | Class | Primary Mechanism | Commonly Reported For | Link |
|---|---|---|---|---|
| Semax | ACTH analogue / nootropic peptide | BDNF upregulation; serotonin, dopamine, and acetylcholine modulation | Focus, memory, mood, neuroprotection | View profile → |
| Selank | Anxiolytic peptide (enkephalin analogue) | GABA-A modulation; BDNF upregulation; anxiolytic without sedation | Anxiety reduction, cognitive clarity | View profile → |
| Dihexa | Angiotensin IV analogue | HGF/c-Met signalling; synaptogenesis; crosses blood-brain barrier | Cognitive enhancement, memory research | Profile coming soon |
Brain-derived neurotrophic factor (BDNF) has emerged as a central molecular target in cognitive peptide research. BDNF supports the survival, growth, and differentiation of neurons and synapses, and its expression is closely linked to learning and memory consolidation. Both Semax and Selank have been shown in preclinical and limited clinical research to upregulate BDNF expression in cortical and hippocampal regions, which is hypothesised to underlie their observed effects on cognitive performance and mood regulation. The BDNF-TrkB signalling axis represents one of the better-characterised pathways through which short peptide fragments can produce downstream neuroplastic effects.
Neurotransmitter modulation across serotonergic, dopaminergic, and GABAergic systems is a second major axis of interest in cognitive support research. Semax has demonstrated effects on serotonin and dopamine turnover in animal models, with downstream implications for motivation, attentional focus, and executive function. Selank's engagement with GABA-A receptor complexes produces anxiolytic activity without the sedative or dependence-forming profile typical of classical benzodiazepines, making it a subject of interest in anxiety-cognitive intersection research. The capacity to reduce background anxiety without impairing arousal is considered relevant to cognitive performance in stress-exposed populations.
Dihexa represents a structurally distinct class of cognitive research compound. As an angiotensin IV analogue, it acts primarily through the hepatocyte growth factor (HGF) and c-Met receptor pathway, which has been implicated in synaptogenesis and dendritic spine formation. Early preclinical data from Washington State University reported potency orders of magnitude greater than BDNF itself in spatial memory tasks, though these findings remain at the animal model stage and have not been replicated in human research trials. Its lipophilicity and ability to cross the blood-brain barrier orally distinguish it mechanistically from intranasal peptides such as Semax and Selank.
Semax is a synthetic heptapeptide derived from the ACTH(4-10) fragment, developed in Russia and approved there for clinical use in stroke and cognitive deficit contexts. Research has investigated Semax for its potential role in BDNF upregulation, enhancement of attentional focus, and modulation of mood via serotonergic and dopaminergic systems. It is most commonly administered intranasally, a route that allows peptide delivery to the brain via olfactory epithelium transport, bypassing systemic degradation. Anecdotal reports suggest improvement in mental clarity and working memory, and it is commonly reported in protocols ranging from 200 to 600 micrograms per dose administered intranasally.
Selank is a synthetic analogue of the endogenous peptide tuftsin, registered as a pharmaceutical in Russia for the treatment of anxiety disorders. Research has investigated Selank for its potential role in anxiolytic activity mediated through GABA-A receptor modulation, alongside BDNF upregulation in hippocampal tissue. Its distinguishing characteristic in the research literature is the absence of sedation, tolerance development, or withdrawal effects observed in classical anxiolytics, making it a compound of interest for anxiety states where preserved cognitive function is prioritised. Commonly reported doses range from 250 to 500 micrograms administered intranasally, typically once or twice daily in research contexts.
Dihexa (also designated PNB-0408) is an angiotensin IV analogue developed at Washington State University with the primary aim of investigating the HGF/c-Met signalling pathway's role in cognitive function and neuroregeneration. Research has investigated Dihexa for its potential role in synaptogenesis and spatial memory enhancement in rodent models of cognitive decline. The compound is notable for its high CNS penetrance relative to molecular weight and its reported potency in preclinical synaptogenesis assays. Human research data remains very limited, and the compound is considered early-stage experimental; no established clinical profile exists at this time.
No established stack protocols documented for this goal at this time.
How does Semax differ from Selank in terms of research targets?
Semax and Selank share BDNF-upregulating activity but operate through different primary mechanisms and produce distinct functional profiles. Semax is more stimulating in character, with documented effects on dopamine and serotonin turnover that correlate with enhanced focus and arousal. Selank's primary characterisation is anxiolytic, working through GABA-A modulation to reduce anxiety without sedation. Research has investigated Semax for its potential role in active cognitive enhancement, while Selank research has concentrated more on anxiety reduction and the cognitive improvements that follow from reduced anxiety load. They are not direct substitutes and are sometimes reported in combination for this reason.
Why is the intranasal route used for Semax and Selank?
The intranasal route provides direct access to the central nervous system via the olfactory epithelium and trigeminal nerve pathways, allowing peptides to bypass the blood-brain barrier that would otherwise limit or prevent their CNS uptake after systemic administration. Both Semax and Selank are relatively small peptides that degrade quickly when administered orally and have poor CNS penetrance by intravenous or subcutaneous routes at practical doses. Intranasal delivery is the route used in Russian clinical research and the basis for their pharmaceutical formulations, making it the reference route for interpreting available efficacy and tolerability data.
What is BDNF and why does it matter for cognition?
Brain-derived neurotrophic factor is a protein belonging to the neurotrophin family that supports the survival and maintenance of neurons and promotes synaptic plasticity — the cellular basis of learning and memory. BDNF acts primarily through the TrkB receptor to activate intracellular signalling cascades involved in long-term potentiation, the molecular process underlying memory formation. Reduced BDNF expression has been associated in research literature with age-related cognitive decline, depression, and neurodegenerative disease states. Compounds that increase BDNF expression — including Semax and Selank — are therefore of research interest as potential modulators of neuroplasticity and cognitive resilience, though the translation from BDNF elevation to measurable cognitive outcomes in humans remains an active area of investigation.
How does Dihexa's research status compare to Semax and Selank?
Semax and Selank are approved pharmaceuticals in Russia with published clinical trial data, established tolerability profiles, and decades of research history. Dihexa is a substantially earlier-stage compound with preclinical data in rodent models but no known human research trials published as of this reference. The mechanistic rationale for Dihexa — HGF/c-Met-mediated synaptogenesis — is scientifically distinct from BDNF-centred approaches and represents a complementary but less validated pathway. Researchers treating Dihexa as equivalent in evidence quality to Semax or Selank would be misreading the state of the literature; the compounds sit at very different points on the research development continuum.