Semax and Selank come from the same Russian research tradition – both were developed at the Institute of Molecular Genetics of the Russian Academy of Sciences, based on short peptide fragments of endogenous hormones. In the research literature they are often treated as a complementary pair: Semax in the field of cognition and neuroprotection, Selank in anxiety and stress research. This article compares the two on the basis of published studies.
Origin compared
Semax is a synthetic heptapeptide derived from a fragment of adrenocorticotropic hormone (ACTH 4-10). It has the amino acid sequence Met-Glu-His-Phe-Pro-Gly-Pro and was originally developed in the context of stroke and ischaemia research.
Selank is also a synthetic heptapeptide, but derived from tuftsin – an endogenous immune peptide (Thr-Lys-Pro-Arg) extended by the tripeptide sequence Pro-Gly-Pro. The same Pro-Gly-Pro extension is found in Semax, giving both peptides increased stability against peptidases.
Mechanisms of action compared
The key difference lies in the neurochemical target system being studied:
- Semax is studied mainly in connection with the BDNF/trkB system. In a study published in 2006 in the journal Brain Research, a single administration of Semax in an animal model led to an up to 1.4-fold increase in BDNF protein levels and a 3-fold increase in BDNF mRNA expression in the hippocampus. BDNF (brain-derived neurotrophic factor) is regarded in research as a central factor in synaptic plasticity and memory formation.
- Selank is studied primarily in connection with the GABAergic system. Several studies by the group around Kolomin, Volkova and Slominsky (including a 2016 paper in Frontiers in Pharmacology) show that Selank influences the expression of genes encoding GABA-A receptor subunits – a possible molecular mechanism for the anxiolytic (anxiety-reducing) effect observed in clinical studies.
Clinical data
For Selank there is a controlled clinical comparison study in humans: in a 2008 study published in Zhurnal Nevrologii i Psikhiatrii, Zozulia, Neznamov and colleagues compared intranasal Selank with the benzodiazepine medazepam in 62 patients with generalised anxiety disorder and neurasthenia. The anxiolytic efficacy of both substances was comparable on standard rating scales – but Selank showed no sedative effect and none of the withdrawal symptoms typical of benzodiazepines.
For Semax the data consist mainly of animal studies and clinical investigations carried out in Russian-speaking countries on stroke, cerebrovascular insufficiency and optic nerve atrophy. For neither peptide is there a Western registration study conducted to international standards (randomised, double-blind, placebo-controlled) – neither is approved as a medicinal product in the EU or the US.
Combination research
Because Semax is studied mainly for activating effects (dopamine, noradrenaline, BDNF) and Selank mainly for calming effects (GABAergic system), the two peptides are often discussed in the research community as a complementary stack – on the assumption that the pro-cognitive effects of Semax can be combined with the anxiety-regulating effect of Selank without Semax’s activating component counteracting Selank’s lack of sedation. Controlled studies directly examining this combination are not yet available.
Direct comparison
| Semax | Selank | |
|---|---|---|
| Origin | ACTH(4-10) fragment | Tuftsin analogue |
| Length | 7 amino acids | 7 amino acids |
| Main mechanism | BDNF/trkB modulation | GABA-A receptor gene expression |
| Research focus | Cognition, neuroprotection | Anxiolysis, stress resilience |
| Clinical human data | mainly observational studies (Russia) | controlled comparison study vs medazepam (n=62) |
Conclusion
Semax and Selank are structurally related but address different neurochemical systems in research: Semax the BDNF/trkB system with a focus on cognition, Selank the GABAergic system with a focus on anxiety and stress regulation. Which peptide is relevant for a particular research question depends on the mechanism being studied.
Both research peptides are available in our shop – lab-tested and COA-certified: Semax and Selank.
Sources & further studies
- Dolotov OV, et al. (2006): Semax, an analog of ACTH(4-10) with cognitive effects, regulates BDNF and trkB expression in the rat hippocampus. Brain Research. DOI: 10.1016/j.brainres.2006.07.108
- Volkova A, Shadrina M, Kolomin T, et al. (2016): Selank Administration Affects the Expression of Some Genes Involved in GABAergic Neurotransmission. Frontiers in Pharmacology. DOI: 10.3389/fphar.2016.00031
- Zozulia AA, Neznamov GG, et al. (2008): Efficacy and possible mechanisms of action of a new peptide anxiolytic Selank in the therapy of generalized anxiety disorders and neurasthenia. Zhurnal Nevrologii i Psikhiatrii Imeni S.S. Korsakova. PMID: 18454096
Note: this article is for information and research purposes only and does not constitute medical advice. Semax and Selank for research are not intended for human consumption or for use in humans.