COGNITIVE & NOOTROPIC / FAQ
Questions From the Literature
Direct, citation-anchored answers to the questions readers most often bring to these two cognitive research peptides.
What is Semax?
Semax is a synthetic heptapeptide — seven amino acids, Met-Glu-His-Phe-Pro-Gly-Pro — derived from the ACTH(4-7) fragment of adrenocorticotropic hormone, with a Pro-Gly-Pro tail added to slow enzymatic breakdown. It is not a hormone and does not trigger cortisol release; it carries the cognitive and adaptive properties of the ACTH fragment without the steroidogenic effect. In rodent research it rapidly upregulates the growth factors BDNF and NGF in a region-specific pattern across the brain [3][4]. In Russia and Ukraine it is approved as a prescription drug for ischemic stroke, TIA, and cognitive impairment; in the US it is classified as an unscheduled research chemical with no approved indication.
What is Semax peptide used for in research?
In published research, Semax is studied primarily for neuroprotection and cognitive performance. Its most-documented effects are in cerebral ischemia models, where it reduces infarct volume and preserves memory [5], and in gene-expression studies where a single intranasal dose changes BDNF and NGF mRNA in the hippocampus, brainstem, cerebellum, and frontal cortex of rats [3]. A 2025 study also found recovery and anti-cell-death effects after spinal-cord injury in mice [1]. Beyond neuroprotection, it inhibits enkephalin-degrading enzymes in human serum in vitro [7], which is thought to contribute to mood and stress-response effects reported anecdotally by users. Russian clinical literature describes use in stroke recovery and optic-nerve disease.
Is Semax a peptide?
Yes. Semax is a synthetic peptide — specifically, a linear heptapeptide consisting of seven amino acids in the sequence Met-Glu-His-Phe-Pro-Gly-Pro. It is synthesized chemically from amino acids; it is not extracted from any natural source. Its design derives from a natural protein sequence (the ACTH(4-7) fragment of adrenocorticotropic hormone), but the full compound including the stabilizing C-terminal tail is a synthetic research molecule with no natural equivalent.
How does Semax work?
Three mechanisms run through the Semax literature. First, it upregulates the neurotrophins BDNF and NGF in the rodent brain — at both the mRNA level [3] and the protein level in the basal forebrain [4] — with a high-affinity binding site (KD 2.4 nM) characterized in rat brain membranes and astrocyte cultures [4]. Second, in human serum in vitro, it inhibits enkephalin-degrading (neprilysin-type) enzymes with an IC50 of roughly 10 micromolar, which could prolong endogenous opioid signaling linked to mood and stress response [7]. Third, in a cerebral ischemia model its neuroprotective effect appears as a broad immunomodulatory and vascular-gene shift affecting over 50% immune genes among all affected transcripts [2], suggesting it acts as a coordinated biological modifier rather than a simple single-target ligand.
What is Selank?
Selank is a synthetic heptapeptide — seven amino acids, Thr-Lys-Pro-Arg-Pro-Gly-Pro — derived from tuftsin (an endogenous immunomodulatory tetrapeptide found in the IgG heavy chain), extended with a C-terminal Pro-Gly-Pro tail for metabolic stability. It is distinctly different from Semax: different core sequence, different primary mechanism, different clinical application. In Russia it is approved as an anxiolytic prescription drug for anxiety-asthenic disorders. In the US it is sold only as an unscheduled research chemical. Its most-documented effects are on the GABAergic system and enkephalin-degrading enzymes [8][7], with additional immunomodulatory activity derived from its tuftsin origin [12].
What does Selank do?
In rodent research, Selank's primary documented effect is anxiolytic: it acts as a positive allosteric modulator of GABA receptor binding [8] and inhibits the enzymes that break down endogenous enkephalins, stabilizing the body's own calming opioid-peptide signaling [7]. In rat frontal cortex it shifted expression of 45 GABA-pathway genes within one hour [10], and when combined with diazepam in a chronic stress model it produced the greatest anxiety reduction [9]. It also increased BDNF expression in the rat hippocampus [11] and modulated cytokine balance in human patients with anxiety disorders [12]. Community reports describe reduced situational anxiety, a calm-but-sharp focus, and a quieter stress response — anecdotal, not clinical evidence.
What is Selank peptide used for in research?
The primary research use of Selank is as a non-benzodiazepine anxiolytic — an anxiety-reducing compound that does not share the sedation, dependence, or cognitive-impairment profile of classical benzodiazepines. Published studies examine it in rodent stress models [9], frontal-cortex gene-expression assays [10], hippocampal BDNF regulation [11], and Russian clinical trials in patients with anxiety-asthenic disorders [12]. A secondary research dimension is immunomodulation, owing to its tuftsin-derived sequence: it has been observed to shift Th1/Th2 cytokine balance and IL-6 expression in human clinical samples [12], characterizing it as an anxiolytic compound with an unusual immune-signaling component.
How does Selank work?
Two primary mechanisms are established in the published literature. First, Selank is a positive allosteric modulator of GABA-receptor binding: it increases [³H]GABA binding in rat brain membranes in a subtype-selective, concentration-dependent way, and this modulation differs from benzodiazepines in that Selank can block the modulatory activity of diazepam and olanzapine at overlapping but distinct binding sites [8]. At the gene level this translates into rapid changes in the expression of dozens of GABA-pathway genes in frontal cortex [10]. Second, Selank inhibits neprilysin-type enzymes that degrade enkephalins, at an IC50 of roughly 20 micromolar in human serum [7], stabilizing endogenous opioid-calming signaling independent of the GABAergic route. Both mechanisms together explain the anxiolytic profile without the sedating GABAergic amplification of benzodiazepines.
Are Semax and Selank the same compound?
No. They share a design feature — both are synthetic heptapeptides stabilized with a C-terminal Pro-Gly-Pro tail — and both inhibit enkephalin-degrading enzymes in human serum, which was documented in the same study [7]. But they are fundamentally different compounds. Semax has an ACTH(4-7) core and acts primarily through neurotrophin upregulation and neuroprotection [3][4]. Selank has a tuftsin core and acts primarily through GABA-receptor modulation and immunomodulation [8][12]. They are studied for different things (neuroprotection and cognitive sharpening versus anxiety and stress reduction), and they have different regulatory profiles in Russian medicine. Conflating them because they look structurally similar is a common error.
Are either Semax or Selank FDA-approved?
No. Neither Semax nor Selank is approved by the FDA for any indication, nor by the EMA. Both hold prescription-drug registration in Russia (and Ukraine, in Semax's case), but that status does not extend to the US or EU. In the United States, both are sold as unscheduled research chemicals — meaning they are not controlled substances, but they are also not medicines, and the material sold for research does not carry the identity, purity, or safety guarantees of a pharmaceutical product. This site describes them in a research context only and makes no clinical recommendation.
What is the difference between using Semax for neuroprotection versus using it as a nootropic?
The distinction is largely one of context and evidence quality. The neuroprotection evidence for Semax is the most mechanistically grounded: documented BDNF and NGF upregulation in rodent brains at the gene and protein level [3][4], reduced infarct volume and improved memory in cerebral ischemia models [5], and a genome-wide mechanism in permanent MCAO [2]. The nootropic use — taking Semax intranasally to sharpen focus, motivation, or verbal fluency in an already healthy person — is what the anecdotal community reports describe, but this has not been the subject of controlled human trials. The pharmacokinetic data (rapid brain penetration within 2 minutes, rapid enzymatic clearance [6]) suggest the peptide reaches the brain quickly, but whether BDNF changes in rodent injury models translate meaningfully to healthy human cognition is a genuine open question.