Selank vs Semax

Selank (Thr-Lys-Pro-Arg-Pro-Gly-Pro, or TKPRPGP) is a synthetic heptapeptide developed by Nikolai Myasoedov and colleagues at the Institute of Molecular Genetics of the Russian Academy of Sciences. It's a structural analog of tuftsin, an endogenous tetrapeptide produced by IgG cleavage in the spleen that participates in immune modulation. The anxiolytic research profile of Selank stems from two primary mechanisms: activity at the GABA-A receptor complex, which is the primary inhibitory neurotransmitter system involved in anxiety regulation, and inhibition of enkephalinase, the enzyme responsible for degrading endogenous enkephalins. By extending enkephalin half-life, Selank effectively amplifies the brain's own anxiolytic peptide signaling without directly binding opioid receptors. In rodent models, Selank has been examined in elevated plus maze and open field paradigms, which are standard anxiety phenotyping assays. It does not produce sedation at research doses studied, distinguishing it from benzodiazepine-class compounds that also act on GABA-A. Selank also shows moderate BDNF upregulation in preclinical studies, though this effect is less pronounced than what's observed with Semax. The compound's immunomodulatory properties, inherited from its tuftsin backbone, have also been studied in models examining natural killer cell activity and cytokine balance. Russian clinical research has examined Selank in anxiety spectrum disorders and stress-related cognitive impairment, with documented intranasal bioavailability supporting its translation from animal models to human studies.

Semax (Met-Glu-His-Phe-Pro-Gly-Pro) is a synthetic heptapeptide analog of the adrenocorticotropic hormone fragment ACTH(4-7), extended with a Pro-Gly-Pro C-terminal addition that stabilizes the molecule and extends its CNS activity. Developed in parallel with Selank at the same Institute of Molecular Genetics, Semax emerged from Soviet research into cognitive-enhancing neuropeptides in the 1980s. Its primary research mechanism is the upregulation of brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF), the core neurotrophins governing neuronal survival, synaptic plasticity, and hippocampal-dependent learning processes. In preclinical models, Semax has been studied extensively in stroke and ischemia paradigms. Animal models of middle cerebral artery occlusion treated with Semax have demonstrated reduced infarct volume and improved recovery of locomotor and cognitive function compared to vehicle controls. The compound's interactions with the melanocortin receptor system, dopaminergic pathways, and serotonin transporter expression have made it a subject of research into attention, memory encoding, and mood-related neurobiology. Its nasal bioavailability and documented CNS penetration following intranasal delivery in rodents have supported a relatively robust body of data from Russian academic and clinical research centers. And while much of the original literature originates from Soviet and post-Soviet institutions, subsequent independent replications have confirmed its BDNF-promoting activity.