What it is
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro (TKPRPGP), molecular formula C₃₃H₅₇N₁₁O₉, molecular weight 751.9 Da, CAS 129954-34-3. It was designed at the Institute of Molecular Genetics of the Russian Academy of Sciences by extending the endogenous immunomodulatory tetrapeptide tuftsin (Thr-Lys-Pro-Arg, cleaved from the Fc region of IgG heavy chain) with a C-terminal Pro-Gly-Pro tripeptide. The Pro-Gly-Pro tail confers resistance to serum and brain aminopeptidases and extends plasma half-life relative to native tuftsin, enabling practical intranasal administration (the approved Russian formulation is a 0.15% nasal-drop solution). Selank is used clinically only in the Russian Federation, where it is marketed as Selank / Селанк and is indicated for generalized anxiety disorder and neurasthenia.
In plain English
Selank is a synthetic seven-amino-acid peptide (TKPRPGP). It was built by taking tuftsin — a natural immune peptide the body clips from antibodies — and adding a short protective tail. That tail stops the body from breaking Selank down too quickly, making it stable enough to spray in the nose and reach the brain. The approved Russian formulation is a 0.15% nasal-drop solution. It was developed at the Institute of Molecular Genetics in Moscow. Selank is used as a prescription drug only in Russia, where it is approved for generalized anxiety disorder and neurasthenia (chronic fatigue combined with anxiety).
How it works
- 01
GABA-A allosteric modulation (gene-expression evidence)
Volkova (2016, Frontiers in Pharmacology) showed that Selank administration to IMR-32 neuroblastoma cells altered expression of GABAergic genes including Gabra6 (GABA-A α6 subunit) and Slc6a13 (GABA transporter GAT-2) in a pattern consistent with positive allosteric modulation rather than direct orthosteric agonism. Kolik (2017) and Semenova (2019) extended this to rat brain regions, observing Gabra6 expression shifts and enhanced diazepam effect in the elevated plus maze when Selank was co-administered — supporting the clinical-trial-level observation (Zozulia 2008) that Selank behaves like an anxiolytic without the sedative/cognitive liabilities of benzodiazepines. No radioligand study has identified a specific Selank binding pocket on the GABA-A receptor, so the 'allosteric modulator' designation is inferred from functional and transcriptional readouts, not from binding data.
In plain English
It may calm the brain's GABA system — but indirectly
GABA is the brain's main calming chemical. Benzodiazepines work by directly activating GABA receptors. Selank works differently: it shifts which GABA-related genes are active, without directly turning on the receptor. Lab studies in human nerve cells and rat brains showed that Selank changed specific GABA receptor and transporter gene activity in a way that suggests it boosts — but doesn't directly trigger — the GABA system. Supporting this: when rats were given Selank plus a small dose of Valium, the calming effect was much bigger than either alone. That boosting behavior fits what scientists call an 'allosteric modulator.' The key gap: no study has found the specific spot on the receptor where Selank docks to produce this effect.
- 02
BDNF upregulation in hippocampus and frontal cortex
Inozemtseva (2008) and Volkova (2016) reported increased BDNF mRNA and protein in rat hippocampus following Selank. Kozlovskii (2019, Bulletin of Experimental Biology and Medicine) showed that Selank (0.3 mg/kg/day IP × 7 days) prevented ethanol-induced reductions in hippocampal and prefrontal-cortex BDNF content and corresponding object-recognition memory deficits. This is the mechanistic basis for claimed nootropic and neuroprotective effects, but is entirely rodent and from the originating-institute group.
In plain English
It raises a brain-growth protein that helps protect memory
BDNF is a protein that helps brain cells grow, survive, and connect — it's closely tied to mood and memory. In rats, Selank raised BDNF levels in the hippocampus and frontal cortex (two key memory and mood areas). In a separate study, Selank prevented alcohol from reducing BDNF and from erasing object memory in rats. This is the basis for calling Selank 'memory-protective.' All of it is animal data from the same Russian lab — no human cognitive trial has been run.
- 03
Monoamine (serotonin, dopamine, norepinephrine) modulation
Semenova (2010, Neurochemical Journal) and follow-up work documented Selank-induced normalization of serotonin, dopamine, and norepinephrine concentrations in mouse hypothalamus, hippocampus, and frontal cortex, with effects most pronounced in anxiety-susceptible strains. Serotonin turnover appears to be the most consistent signal and is proposed as a contributor to the mood-stabilizing component of the anxiolytic profile.
In plain English
It normalizes mood-related brain chemicals in stressed animals
In anxiety-prone mice, Selank moved serotonin, dopamine, and norepinephrine levels in key brain areas closer to normal. Serotonin was the most consistent signal. This is proposed as part of why Selank may stabilize mood. All of it is rodent data — the effect was most pronounced in strains of mice bred to be anxious, which suggests the drug may mainly correct an abnormal baseline rather than acting on a normal one.
- 04
Enkephalinase inhibition
Kozlovskaya (2003) reported that Selank produced robust anxiolytic effects in BALB/c mice (which express high enkephalin-degrading enzyme activity) but not in C57BL/6 mice (low activity), consistent with Selank preserving endogenous enkephalins by inhibiting their degradation. This provides a plausible mechanism for an opioid-system contribution to the anxiolytic effect distinct from the GABAergic arm. No human enkephalin pharmacodynamics have been measured.
In plain English
It may preserve the body's own natural calming molecules
The body makes its own natural calming molecules called enkephalins. An enzyme called enkephalinase breaks them down. In mice with lots of this enzyme, Selank strongly reduced anxiety. In mice with low levels of it, Selank barely worked. This suggests Selank works partly by slowing down the breakdown of the body's own calming chemicals — essentially letting them last longer. This is a separate anxiety-relief pathway from the GABA effect. No human data has tested this.
- 05
Immunomodulation and cytokine effects (tuftsin pharmacology)
Because Selank contains the complete tuftsin sequence at its N-terminus, it retains tuftsin-like engagement of macrophage/neutrophil tuftsin receptors. Uchakina (2008) reported IL-6 suppression in patients with depressive disorder who had baseline IL-6 elevation, without cytokine changes in healthy controls — characterized as 'adaptogenic' immunomodulation. Kolomin (2011) reviewed T-helper cytokine rebalancing and reduced TNF-α signaling. These effects link the CNS-anxiolytic profile to the peripheral immune system and are one of the more distinctive features of the molecule compared with benzodiazepines.
In plain English
It inherits immune effects from the tuftsin part of its structure
The first four amino acids of Selank's sequence are identical to tuftsin — a natural immune peptide the body clips from antibodies to activate immune cells. Because of this, Selank can bind to immune cells the way tuftsin does. In depressed patients with elevated inflammation (high IL-6), Selank lowered that marker — but did nothing in healthy people. This is called 'adaptogenic' because it only seems to correct an abnormality, not suppress a healthy immune system. This immune angle makes Selank different from benzodiazepines, which have no immune effects at all.
- 06
What is NOT known about the mechanism
No Selank-specific receptor has been molecularly identified. The allosteric-modulator designation is functional/transcriptional, not structural. Intranasal human pharmacokinetics (Cmax, Tmax, CNS penetration, half-life) are not characterized in Western peer-reviewed literature. The extent to which the reported CNS effects in rodents reflect central vs peripheral (tuftsin-receptor-mediated vagal / immune) signaling has not been dissected. Receptor pharmacology, PK, and blinded mechanistic replication are the three missing pillars that would move the grade upward.
In plain English
What we still don't know about how it works
No one has identified the specific molecular target Selank binds to. The 'GABA booster' label is based on changes in gene activity, not on finding an actual receptor site. How much Selank reaches the brain when sprayed in the nose hasn't been published in any Western journal. It's also unknown whether the calming effects seen in rodents come from direct brain action or from signaling through the immune system. Those three gaps — molecular target, nose-to-brain delivery, and central vs peripheral action — are the main reasons the evidence grade stays capped at C.