Selank vs Semax: two nootropic peptides compared

Research context (RUO): Selank and Semax are two synthetic peptides of Russian origin studied in laboratory research into anxiolytic and cognitive mechanisms respectively. Both are supplied exclusively for in-vitro laboratory research and not for human or animal use.

Selank vs Semax: two nootropic peptides compared

Anyone who delves into nootropic peptides soon comes across the comparison Selank vs Semax : two short peptides that were both developed in Russia, both administered via the nasal mucosa in research and both associated with effects on the central nervous system. Yet they are fundamentally different molecules with a different origin, a different mechanism and a different research focus. Selank is derived from the immune peptide tuftsin and is studied primarily as an anxiolytic (anxiety-reducing), whereas Semax is derived from the hormone ACTH and is investigated mainly for cognitive and neuroprotective properties. This pillar sets the differences and similarities clearly side by side, so that researchers can properly distinguish the two peptides from each other.

What is Selank?

Selank is a synthetic heptapeptide (seven amino acids) developed at the Institute of Molecular Genetics and the V. V. Zakusov Research Institute of Pharmacology in Moscow. It is a stabilised analogue of tuftsin, a naturally occurring immunoregulatory tetrapeptide released from the antibody immunoglobulin G. An amino-acid tail (Pro-Gly-Pro) has been added to the tuftsin fragment to stabilise the molecule, so that Selank remains intact longer in research than the rapidly degrading natural tuftsin. In the scientific literature, Selank is placed mainly in the category of the anxiolytic peptides: compounds associated in animal models with a reduced anxiety and stress response without the sedative side effects that characterise classic tranquillisers.

What is Semax?

Semax is likewise a synthetic peptide of Russian origin, but with an entirely different lineage. It is an analogue of the fragment ACTH(4-10), a part of the hormone adrenocorticotropin (ACTH). Whereas the full ACTH molecule prompts the body to produce cortisol, the ACTH(4-10) fragment lacks that hormonal action and is said to retain mainly the effects on the nervous system. Semax too has a Pro-Gly-Pro tail attached to stabilise the molecule. In research, Semax is studied primarily as nootropic and neuroprotective peptide, with a focus on learning, memory, attention and the protection of nerve cells after oxygen deprivation (ischaemia). More about this line of research is set out in our pillar Semax research.

Selank vs Semax: the mechanisms side by side

The biggest difference between the two peptides lies in the biological pathway through which they appear to act in research. Both ultimately touch the neurotrophin system — the proteins such as BDNF and NGF that support the growth and survival of nerve cells — but they approach that system from different angles.

• Selank — GABA and tuftsin route: Selank is associated in research with the GABAergic system, the brain's principal inhibitory signalling system. In a 2017 study (Frontiers in Pharmacology), Selank influenced the expression of genes involved in GABAergic neurotransmission in neuronal cells. As a tuftsin analogue, an immunomodulatory component is also being investigated. In a 2019 rat study, Selank regulated BDNF levels in the hippocampus and prefrontal cortex and was associated with protection against ethanol-induced memory impairment.
• Semax — ACTH and neurotrophin route: Semax is strongly associated in research with a direct upregulation of neurotrophins. Studies show that Semax influences the expression of BDNF and NGF and their receptors (such as trkB) in the brains of rats, with time- and region-dependent effects in the hippocampus, frontal cortex and retina. This neurotrophin activation is regarded as a possible basis for the cognitive and neuroprotective effects reported in animal models.

In short: in research, Selank leans more on anxiety regulation via GABA and immune modulation, while Semax leans more on memory and neuroprotection via direct neurotrophin activation. Both touch on BDNF, but from a different starting point.

What are Selank and Semax studied for?

The research focus of the two peptides reflects their mechanism. The overview below summarises the main research areas as described in preclinical and some clinical studies — each attributed to the research, not to the reader.

• Selank — anxiety and stress: researchers study Selank mainly as an anxiolytic. Russian studies described it as a candidate in generalised anxiety and neurasthenia, with the effect attributed to modulation of GABA and of the balance between stress and recovery systems.
• Selank — immune and neurotrophin: due to the tuftsin origin, an immunomodulatory profile is also studied, alongside the reported regulation of BDNF in memory-relevant brain regions.
• Semax — cognition and attention: Semax is studied for learning, memory and attention, with neurotrophin activation as the proposed mechanism.
• Semax — neuroprotection: a major line of research focuses on protection of nerve tissue after ischemia (oxygen deficiency), with Semax being associated in studies with increased neurotrophin expression after cerebral ischemia.

Those who want to explore the broader category will find in our pillar cognitive peptides an overview of how these compounds relate to each other.

Selank vs Semax in laboratory research: handling & dissolving

Both peptides are supplied as freeze-dried (lyophilised) powder that must be reconstituted before in-vitro use. Because they are short, relatively stable peptides, comparable handling guidelines apply: reconstitute with a suitable liquid, store cool and avoid light. Which liquid is suitable and why is explained in our pillars reconstitute peptides and which liquid to dissolve peptides in. Correct reconstitution and storage are important for the reliability and reproducibility of laboratory results.

Quality & purity

For a meaningful comparison of two peptides in research, the purity of the starting material is crucial — impurities can distort results. Every relevant batch of Selank and Semax at Peplife is independently HPLC-tested by an external laboratory; the certificate of analysis (CoA) is publicly verifiable per batch. This way, researchers know exactly what is in the vial before they study the two peptides side by side. Background on our quality process is in why we rejected a batch.

Frequently asked questions about Selank vs Semax

What is the main difference between Selank and Semax?
The origin and focus differ: Selank is a tuftsin analogue studied in research mainly as an anxiolytic (anxiety-reducing), whereas Semax is an ACTH(4-10) analogue investigated mainly for cognition and neuroprotection. Both are intended exclusively for laboratory research.

Do Selank and Semax work via the same mechanism?
Not primarily. Selank is associated in research with the GABAergic system and immunomodulation, Semax with the direct activation of neurotrophins such as BDNF and NGF. Both ultimately touch BDNF, but via a different starting point.

Are Selank and Semax both Russian peptides?
Yes. Both were developed in Russian research institutes and are synthetic peptides with an added Pro-Gly-Pro tail for stability. Their molecular basis differs, however: tuftsin in Selank, an ACTH fragment in Semax.

Can you research Selank and Semax together?
In some research designs, complementary peptides are studied in combination, but Peplife gives no usage or dosing advice. Both peptides are supplied exclusively for in-vitro laboratory research, not for human or animal use.

Which of the two is most studied for cognition?
Semax has the largest body of research on learning, memory, attention and neuroprotection after ischaemia. Selank, by contrast, is most often studied in the context of anxiety and stress, although there is also Selank research into memory and BDNF.

Where can I buy Selank and Semax for research?
Both are available at Peplife as HPLC-tested, freeze-dried powder for laboratory research: Buy Selank and Buy Semax.

Read more & research at Peplife

• Research Selank at Peplife
• Research Semax at Peplife
• View all cognitive peptides
• Selank research: the anxiolytic tuftsin analogue
• Semax research: the cognitive ACTH analogue
• Cognitive peptides: the complete overview

Sources: Selank & BDNF, ethanol model (Bull Exp Biol Med, 2019) · Selank & GABAergic gene expression (Frontiers in Pharmacology, 2017) · Semax & NGF/BDNF gene expression (2010) · Semax regulates BDNF/trkB in the hippocampus (2006)

Research Use Only. All products are supplied exclusively for in vitro laboratory research. Not intended for diagnostic or therapeutic use in humans or animals, and not approved by the EMA or FDA.