Intro
Semax and Selank are two synthetic heptapeptides that are frequently discussed together in cognitive and neuropeptide research. Both were developed within the Russian regulatory-peptide research tradition, and both have been examined in laboratory models focused on central nervous system signalling, adaptive stress response, and comparative peptide pharmacology. Despite that overlap, the two compounds are structurally distinct and are studied for different primary mechanisms. Semax is most often positioned in the literature as a neurotrophic and transcriptomic research tool, while Selank is more commonly examined in GABAergic, enkephalin-related, and neuroimmune signalling contexts.
At Pepcore, both compounds are supplied as research-grade lyophilized peptides for laboratory work. Semax 10 mg, Selank 10 mg, NA-Semax 10 mg, and NA-Selank 10 mg are supplied at 99% HPLC purity with Certificate of Analysis included. All products are supplied for research use only.
Origins
Semax carries the amino acid sequence Met-Glu-His-Phe-Pro-Gly-Pro and is a synthetic analogue of the ACTH(4-10) fragment. The peptide was engineered to retain the neurotropic signalling interest of the parent ACTH fragment while avoiding adrenocortical activity in experimental settings. Published work has examined Semax as a stable short regulatory peptide suitable for studying neurotrophin expression, melanocortin-related signalling, and monoaminergic pathway interactions in laboratory models.
Selank carries the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro and is derived from the endogenous tetrapeptide tuftsin. The addition of the Pro-Gly-Pro extension improves resistance to enzymatic degradation and supports its use in central nervous system and neuroimmune research workflows. In published literature, Selank is more often framed as a research compound for GABAergic modulation, stress-response pathway studies, and enkephalin-related signalling than as a primarily neurotrophic peptide.
Semax Pathways
The most consistently documented Semax mechanism in the literature is neurotrophic factor regulation. Research has shown that Semax can increase expression of BDNF- and NGF-related pathways in rat brain models, with region-specific effects observed in hippocampal and basal forebrain tissue. Shadrina and colleagues reported rapid induction of neurotrophin mRNAs in rat glial cultures after Semax exposure, while Dolotov and colleagues later documented Semax-specific binding together with increased BDNF protein levels in rat basal forebrain tissue. Agapova and co-workers extended these findings by describing different temporal patterns of BDNF and NGF expression across hippocampus, brainstem, and retina after intranasal administration.
This body of work has made Semax a useful reference compound in research on neurotrophic signalling, neuronal plasticity, and survival-pathway transcription. In practice, Semax is most relevant when the experimental question involves BDNF or NGF regulation, pathway timing across brain regions, or comparative studies of short ACTH-derived regulatory peptides.
Published research has also examined Semax in relation to melanocortin-system signalling. The compound is often discussed as interacting with melanocortin-related pathways relevant to synaptic signalling and regulatory-peptide biology. That framing is safer and more consistent with the literature than overspecifying a single receptor claim when discussing customer-facing research content.
A further layer of Semax research concerns monoaminergic pathway modulation. Eremin and colleagues reported measurable effects on serotonergic turnover markers in rodent striatal tissue and showed that Semax can modulate dopaminergic system responses under stimulated conditions. These findings do not position Semax as a direct dopamine agonist; rather, they support its use in comparative research on how short neuropeptides influence broader signalling environments involving serotonin, dopamine, and neurotrophin-related pathways.
Semax Uses
In laboratory contexts, Semax has been studied in relation to BDNF and NGF expression models, melanocortin-related signalling, ischemia-model signalling, transcriptomic response mapping, monoaminergic pathway interaction studies, and broader cognitive-pathway research. The literature most consistently positions it as a tool for studying how a short regulatory peptide can influence neurotrophic signalling and downstream neuronal-response pathways under defined experimental conditions.
Selank Pathways
Selank is most strongly associated with GABAergic modulation in the published literature. Semenova and colleagues examined its molecular activity in relation to GABA-A receptor signalling and described a distinct allosteric interaction profile in comparative neurochemistry research. This has made Selank a useful compound for studies focused on inhibitory neurotransmission, receptor modulation, and non-benzodiazepine comparative GABAergic signalling.
Selank has also been examined at the transcriptional level. Filatova and co-workers reported changes in expression of multiple genes linked to GABAergic neurotransmission after Selank exposure in experimental systems, including genes associated with receptor subunits and related signalling machinery. These results suggest that Selank research may extend beyond immediate receptor modulation into broader regulation of inhibitory signalling networks, although the magnitude and context of these effects remain model-dependent.
Another important area is the enkephalin-related pathway. Kost and colleagues examined the effect of both Semax and Selank on enkephalin-degrading enzymes and found that both peptides inhibited the same enzyme systems in human serum, with Semax generally showing somewhat stronger potency and Selank still demonstrating meaningful inhibitory activity. Additional Selank-focused work connected this pathway to anxiety-model research and longer leu-enkephalin half-life in laboratory and comparative clinical research settings. For Pepcore purposes, the safe takeaway is that Selank is a useful reference compound for studying how short peptides may influence endogenous enkephalin-related signalling through enzyme inhibition.
Selank also differs from Semax in its neuroimmune framing. Because of its tuftsin-derived origin, it is frequently discussed in relation to cytokine signalling, immune-cell communication, and stress-linked neuroimmune pathway models. This does not make it an immune therapeutic claim; it simply places Selank in a broader research category than Semax, spanning both neurotransmission and immune-signalling questions.
Selank Uses
Published research has examined Selank in GABAergic receptor modulation studies, comparative anxiety-pathway research models, enkephalin-related signalling, neuroimmune pathway studies, stress-response signalling, and transcriptional mapping of inhibitory neurotransmission networks. Relative to Semax, Selank is more relevant when the primary question is inhibitory signalling balance, peptide effects on adaptive-response models, or comparative work involving GABAergic compounds and regulatory peptides.
NA Variants
Pepcore also supplies the acetylated variants NA-Semax 10 mg and NA-Selank 10 mg. These are the N-acetyl forms specifically supplied in the Pepcore catalog.
NA-Semax is the N-terminally acetylated analogue of Semax. The main rationale for this modification is improved resistance to aminopeptidase-mediated degradation at the N-terminus. Research on Semax analogues has shown that changes at the N-terminal region can substantially alter degradation behaviour in biological matrices. Additional coordination-chemistry work has shown that acetylation also changes Semax metal-binding behaviour, which has made NA-Semax relevant in comparative studies examining how terminal modification influences stability, copper coordination, and downstream signalling properties.
NA-Selank is the N-terminally acetylated analogue of Selank. Published research specifically dedicated to NA-Selank is more limited than the parent Selank literature, but the general peptide-chemistry logic is straightforward: N-terminal acetylation can reduce exopeptidase susceptibility and extend effective stability in laboratory models. For research design, that makes NA-Selank most useful when the experiment requires longer exposure windows or when the role of terminal modification itself is part of the comparison.
For both NA variants, the most accurate customer-facing framing is that they preserve the parent compound family while offering a more stability-oriented research profile. They should be described as adjacent research tools, not as automatically superior versions of the parent peptides.
Comparing Them
The clearest way to compare Semax and Selank is by their dominant research pathways.
Semax is more appropriate when the core question involves neurotrophic factor expression, transcriptomic response to regulatory peptides, melanocortin-related signalling, or monoaminergic interaction in cognitive-pathway models. It is best understood as a neurotrophic and signalling-oriented research peptide.
Selank is more appropriate when the core question involves GABAergic modulation, enkephalin-related signalling, adaptive stress-response pathways, or neuroimmune signalling. It is best understood as a GABAergic and regulatory-pathway research peptide with a broader inhibitory and neuroimmune framing.
The shared point of overlap is enkephalinase inhibition. Both compounds have been shown to inhibit enkephalin-degrading enzymes, but that overlap does not erase their larger mechanistic differences. For most laboratory designs, they are better treated as complementary comparators than as near-substitutes.
For researchers studying both pathway families in parallel, separate vials allow independent dosing and cleaner experimental control. Pepcore's full Cognitive Research category also includes related compounds used in adjacent central nervous system and regulatory-peptide studies.
Quality and Sourcing
For Semax, Selank, NA-Semax, and NA-Selank, the usual research-grade quality markers matter: HPLC purity, lot-specific documentation, structural identity confirmation, and stable lyophilized presentation. Pepcore supplies these peptides at 99% HPLC purity, with COA included and fast EU shipping. For researchers running reproducible in vitro or preclinical work, those quality controls are as important as the literature profile itself.
Conclusion
Semax and Selank are frequently discussed together, but the published research supports treating them as mechanistically distinct compounds. Semax is primarily positioned around neurotrophic factor expression, transcriptomic regulation, and broader signalling studies linked to ACTH-derived peptide biology. Selank is primarily positioned around GABAergic modulation, enkephalin-related signalling, and neuroimmune pathway research linked to its tuftsin-derived origin.
The acetylated forms NA-Semax and NA-Selank add a stability-focused layer to that comparison by reducing susceptibility to enzymatic degradation in laboratory settings. For cognitive and central nervous system research programs, the right choice depends less on which peptide is stronger and more on which signalling pathway the model is designed to interrogate.
All four compounds are supplied by Pepcore for research use only.
References
Shadrina MI, Andreeva LA, Myasoedov NF, et al. Rapid induction of neurotrophin mRNAs in rat glial cell cultures by Semax. Neuroscience Letters, 2001. https://pubmed.ncbi.nlm.nih.gov/11457573/
Dolotov OV, Karpenko EA, Seredenina TS, et al. Semax, an analogue of adrenocorticotropin (4-10), binds specifically and increases levels of brain-derived neurotrophic factor protein in rat basal forebrain. Journal of Neurochemistry, 2006. https://pubmed.ncbi.nlm.nih.gov/16635254/
Agapova TY, Shadrina MI, Slominsky PA, et al. Neurotrophin gene expression profile is differentially regulated by Semax depending on the part of the rat brain. Neuroscience Letters, 2007. https://pubmed.ncbi.nlm.nih.gov/17353092/
Eremin KO, Kudrin VS, Rayevsky KS, et al. Semax activates serotonergic and dopaminergic brain systems in rodents. Neurochemical Research, 2005. https://pubmed.ncbi.nlm.nih.gov/16362768/
Semenova TP, Kozlovskaya MM, Andreeva LA, et al. Peptide-based anxiolytics: the molecular aspects of heptapeptide Selank biological activity. Protein and Peptide Letters, 2018. https://pubmed.ncbi.nlm.nih.gov/30255741/
Filatova EV, Kasian AP, Kolomin TA, et al. GABA, Selank, and olanzapine affect the expression of genes involved in GABAergic neurotransmission in IMR-32 cells. Frontiers in Pharmacology, 2017. https://pubmed.ncbi.nlm.nih.gov/28293190/
Kost NV, Sokolov OY, Gabaeva MV, et al. Inhibitory effect of Semax and Selank on enkephalin-degrading enzymes in human serum. Bulletin of Experimental Biology and Medicine, 2001. https://pubmed.ncbi.nlm.nih.gov/11443939/
Kost NV, Sokolov OY, Gabaeva MV, et al. The possible mechanism of anxiolytic activity of Selank. Bulletin of Experimental Biology and Medicine, 2001. https://pubmed.ncbi.nlm.nih.gov/11550013/
Kozlovskaya MM, Nesmeyanov PP, Andreeva LA, et al. Effects of Selank on the behavior of rats and activity of enkephalin-degrading enzymes. Bulletin of Experimental Biology and Medicine, 2002. https://pubmed.ncbi.nlm.nih.gov/12432865/
Rojo NG, Dokudovskaya SS, Streltsov SA, et al. N-terminal acetylation alters the copper(II)-binding properties of Semax. Journal of Inorganic Biochemistry, 2016. https://pubmed.ncbi.nlm.nih.gov/27586814/
Research Use Only Disclaimer
All peptides described in this article, including Semax, Selank, NA-Semax, and NA-Selank, are supplied strictly for in vitro and preclinical research purposes only. They are not approved for human or veterinary use. They are not medicines, food supplements, or cosmetic ingredients. This article is intended for researchers and laboratory personnel and does not constitute medical, pharmacological, or clinical advice.
