Nootropic Neuropeptides Research — Semax, Selank & Cerebrolysin Comparison

**Semax** (ACTH 4-7 Pro-Gly-Pro analog, MW ~868 Da): The parent ACTH 4-10 heptapeptide was identified in the 1970s as the melanocortin receptor-independent cognitive-active fragment of ACTH. Semax (the Pro-Gly-Pro C-terminal extension) was developed to increase metabolic stability. Semax's primary published research mechanisms include: (1) BDNF and trkB upregulation in hippocampus and frontal cortex in rodent models; (2) dopamine turnover modulation in striatum; (3) upregulation of learning-related genes in the hippocampus in passive-avoidance and Morris water maze models. Semax is approved in Russia for ischemic stroke and optic nerve atrophy. DMV Research carries Semax as a lyophilized research peptide. Selank's mechanistic complement (see below) is why Semax + Selank is a commonly researched nootropic combination (covered in depth in the Selank+Semax stack page).

**Selank** (tuftsin analog TKPRPGP, MW ~751 Da): Tuftsin (Thr-Lys-Pro-Arg) is an endogenous tetrapeptide from IgG that modulates innate immunity and has centrally-mediated anxiolytic effects. Selank (with the Pro-Gly-Pro C-terminal extension for stability, same motif as Semax) is the Academician Meshcherskiy Valdimir Valdimirovich-developed tuftsin analog. Selank's published mechanisms include: (1) GABAergic modulation — potentiates GABA-A receptor function, producing anxiolytic effects comparable to benzodiazepines in rodent models (elevated plus maze, open field) WITHOUT sedation or dependence in acute studies; (2) IL-6 and IL-4 modulation — anti-inflammatory immunomodulatory effects, which may underlie mood-adjacent effects; (3) BDNF upregulation (shared with Semax, suggesting complementarity). Selank is approved in Russia for anxiety disorders. The Semax+Selank combination is studied for cognitive + anxiolytic co-effects.

**Cerebrolysin** is mechanistically distinct from Semax and Selank: it is not a single defined peptide but a standardized protein hydrolysate (4 mL ampoule; ~25% low-molecular-weight peptides, ~75% amino acids) from porcine brain. Its neurotrophic activity is attributed to peptide fragments with BDNF-like, NGF-like, CNTF-like, and GDNF-like activity. Cerebrolysin has the largest clinical trial record of the three: published randomized controlled trials in Alzheimer's disease (Muresanu 2008, Alvarez 2011), vascular dementia, and ischemic stroke have shown functional improvement signals; a Cochrane review (2010) concluded available evidence suggested positive cognitive effects in Alzheimer's, though it noted methodological limitations. Cerebrolysin is approved or in clinical use in multiple European and Asian countries. It is not FDA-approved. For researchers: Cerebrolysin is available as an injectable solution (standard research form); Semax and Selank are available as lyophilized peptides for reconstitution. All three are research use only.