Semax emerged from a deceptively simple observation: the ACTH molecule contains two distinct functional domains — a hormonal segment (residues 1-3) that stimulates corticosteroid release, and a neurotrophic segment (residues 4-10) that affects brain function independently of adrenal activation. By isolating and stabilizing the neurotrophic fragment, Russian researchers created a peptide with cognitive and neuroprotective properties free from hormonal side effects.
Structure and Design
Semax has the sequence Met-Glu-His-Phe-Pro-Gly-Pro. The core heptapeptide ACTH(4-10) (Met-Glu-His-Phe-Arg-Trp-Gly) was modified to improve metabolic stability while retaining neurotrophic activity. The C-terminal Pro-Gly-Pro tripeptide extension — the same stabilizing motif used in Selank — extends the peptide's half-life and CNS bioavailability.
Neurotrophic Effects: BDNF and NGF
Semax's most robust documented effect is upregulation of brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF). In rodent studies, intranasal Semax administration increased BDNF mRNA expression in hippocampus, cortex, and basal forebrain within hours. This neurotrophic response underlies the peptide's pro-cognitive effects — BDNF is the principal mediator of synaptic plasticity, the cellular basis of learning and memory (Dolotov et al., 2006; PMID: 16996072).
Cognitive Enhancement Research
Semax improved performance across multiple cognitive paradigms in rodent studies: Morris water maze (spatial memory), passive avoidance (associative learning), and operant conditioning tasks. The peptide enhanced both acquisition (learning) and retention (memory) phases. Notably, cognitive effects were most pronounced in aged animals and those with experimentally induced cognitive deficits, suggesting particular utility in impaired-state research models.
Cerebrovascular and Stroke Research
Semax has been studied extensively in cerebral ischemia models. In MCAO (middle cerebral artery occlusion) rat models of stroke, Semax reduced infarct volume, improved neurological deficit scores, and enhanced post-ischemic recovery. The mechanism appears to involve both direct neuroprotection (BDNF-mediated anti-apoptotic signaling) and improved cerebrovascular flow dynamics (Gusev et al., 1997; PMID: 9463034).
In Russia, Semax has been approved for clinical use in stroke rehabilitation — one of the few peptide nootropics to achieve regulatory approval in any jurisdiction.
Gene Expression Profile
Transcriptomic studies have shown that Semax modulates expression of genes involved in neurotransmitter systems (glutamatergic, dopaminergic, serotonergic), immune response, vascular function, and oxidative stress defense. The breadth of gene expression changes suggests Semax acts as a pleiotropic modulator rather than a single-target compound.
Research-Grade Semax
Semax is available in 10mg lyophilized vials at researchvials.com.
References
- Dolotov OV, et al. Semax, an analog of ACTH(4-10) with cognitive effects, regulates BDNF and trkB expression in the rat hippocampus. Brain Res. 2006;1117(1):54-60. PMID: 16996072
- Gusev EI, et al. Neuroprotective effects of Semax in acute cerebral ischemia. Zh Nevrol Psikhiatr Im S S Korsakova. 1997;97(6):26-34. PMID: 9273192