Selank

Selank is a seven-amino-acid peptide from the same Moscow institute that produced Semax, built on the same principle and around a very different core. Its active part is tuftsin — a four-residue fragment, threonine-lysine-proline-arginine, cut from an antibody molecule — with the familiar Pro-Gly-Pro tail attached to protect it from enzymes.

Tuftsin itself belongs to immunology rather than neuroscience. It is released from the heavy chain of immunoglobulin G and stimulates the cells that engulf debris and pathogens. That a fragment of an antibody should have anything to do with anxiety is not obvious, and it is the reason this compound is interesting.

The connection runs through a field that barely existed when the work began. Immune signalling molecules are now known to act in the brain and to influence mood and behaviour, and communication between the immune and nervous systems is an established area of study. Selank was developed before that framework was widely accepted, which makes it an unusual case of an empirical finding arriving ahead of the explanation.

• An immune fragment with central activity: A sequence from an antibody producing behavioural effects is a concrete example of immune–nervous system crossover, a subject that has only recently become mainstream.

• GABA signalling: Published work reports effects on the brain's principal inhibitory neurotransmitter system — the one that dampens neural activity, and the target of most conventional anxiety medication.

• Anxiety without sedation: Most compounds that reduce anxiety through GABA also cause drowsiness and tolerance. Reports that this one does not is the specific claim that makes it worth investigating.

• Shared stabilisation chemistry: It uses the same Pro-Gly-Pro tail as Semax on a completely different core, which makes the pair a demonstration of how a stabilising element can be reused independently of the active sequence.

Neural activity is balanced between signals that excite neurons and signals that inhibit them. GABA is the main inhibitory transmitter in the brain: when it binds its receptor, the neuron becomes harder to fire. Most anxiety medication works by making that receptor respond more strongly to the GABA already present, which is effective and also why such drugs cause sedation and lose effect over time.

Selank is reported to influence this system differently — not by acting on the receptor directly, but by affecting the expression of its components and the metabolism of the transmitter. If correct, that is a meaningfully different kind of intervention: changing the machinery rather than amplifying the signal, which would account for reports of reduced anxiety without the drowsiness that usually accompanies it.

There is a second, better-established strand. Selank has been reported to slow the breakdown of enkephalins, short peptides the brain produces that act on opioid receptors and are involved in regulating mood and stress. A compound that extends the life of a signal the brain already makes is doing something different again from one that adds a signal of its own, and both accounts appear in the literature on this peptide.

Like Semax, Selank is registered as a medicine in Russia and supported by a body of clinical and laboratory work there, including comparisons with conventional anxiety medication. Animal studies showing anxiety-related behavioural effects have been published.

Most of the work originates from the tradition that developed it, much of it published in Russian, with limited independent replication. It holds no approval in the UK, EU or US and is supplied for laboratory research only. It is a registered medicine in Russia with decades of study behind it, and the tool for an unusual question: how a fragment of an antibody comes to have central activity at all.

Semax is the sibling compound — same institute, same stabilising tail, a hormone fragment rather than an immune one at its core. The pair are the clearest illustration of the design philosophy behind this whole research tradition.

Cerebrolysin and Pinealon sit nearby in that tradition, one a brain-derived mixture and the other a short bioregulator peptide. The reported effect on enkephalin breakdown also places this peptide within reach of opioid receptor research, where Dermorphin is the standard selective tool.