Was the BDNF work done in humans?

No. It was conducted in rats, using intranasal administration.

Does raising BDNF expression prove an effect?

No. Expression is upstream of function, and a measurable change in a rodent brain region does not establish an outcome in an organism or a species.

Selank (Tuftsin Analogue)

Selank and BDNF: What the Studies Measured

JMWritten & reviewed by Jack Muncaster · Founder, UK PeptidesLast reviewed 2026-08-232 cited sources

Inozemtseva and colleagues reported in Doklady Biological Sciences in 2008 that intranasal administration of Selank regulates BDNF expression in the rat hippocampus. This is a gene- and protein-expression measurement in a rodent model, not a behavioural or clinical endpoint.

Key facts

Publication: Dokl Biol Sci, 2008
PMID: 18841804
First author: Inozemtseva LS
Route studied: Intranasal
Region: Hippocampus
Measured: BDNF expression
Model organism: Rat

Why BDNF appears in so much peptide research

Brain-derived neurotrophic factor supports neuronal survival, differentiation and synaptic plasticity, signalling through the TrkB receptor. It is among the most measured molecules in neuroscience because expression changes are technically accessible and because BDNF sits downstream of many interventions. That accessibility is also why BDNF results should be read carefully — a great many things move it.

What this study reported

Intranasally administered Selank was reported to regulate BDNF expression in the rat hippocampus. The intranasal route is significant in itself: it is used in rodent work partly because it offers a path to the central nervous system that partially bypasses systemic circulation, which matters for a peptide unlikely to cross the blood-brain barrier efficiently.

Research material referenced

Selank 10mg — third-party HPLC tested

View — £24.99

Expression is upstream of effect

Demonstrating that a compound changes BDNF expression in rat hippocampus establishes that it does something measurable to that pathway. It does not establish a functional consequence, and it does not establish one in another species. The gap between an expression change and an outcome is where a great deal of peptide literature quietly overreaches, and it is worth holding onto here.

The parallel with Semax

Semax, from the same institute and built by the same design method, also has a BDNF literature — including work in Brain Research and Doklady Biological Sciences from the same period and partly overlapping author groups. Two structurally unrelated peptides sharing a stabilising motif and both reported to move BDNF is worth noting as a pattern in the research programme rather than as independent confirmation of either.

Later work

A 2019 study in the Bulletin of Experimental Biology and Medicine examined Selank in a model of ethanol-induced memory impairment, extending the behavioural literature. It remains preclinical, as does essentially all mechanistic work on this compound.

Extended research context

The Selank (Tuftsin Analogue) deep dive

Deep dive: preserving a signal rather than supplying one

Selank's most specifically characterised activity is not receptor binding. Work published in the Bulletin of Experimental Biology and Medicine in 2001 and 2002 reported that it inhibits enkephalin-degrading enzymes, measured directly on plasma enkephalinase activity, thereby extending the half-life of endogenous enkephalins rather than acting at opioid receptors itself. That distinction is routinely muddled and it matters: an agonist activates the receptor wherever the drug reaches, at whatever concentration is given, while a degradation inhibitor only lets the ligand the body is already releasing persist longer. The effect is bounded by endogenous release and occurs only where that release happens. The same logic underlies DPP-4 inhibitors in the incretin field, which prolong native GLP-1 rather than supplying an analogue - and instructively, that class produces much smaller effects than the receptor agonists do.

Deep dive: what the sequence does and does not contain

TKPRPGP is unusual among research peptides for what is absent from it. There is no cysteine, so no disulfide bonds form or scramble and no reducing agent is needed. There is no methionine, so the thioether oxidation that adds 16 Da and dominates handling guidance for MOTS-c and Semax does not apply. There is no asparagine or glutamine either, ruling out deamidation. What remains is straightforward hydrolysis, and three prolines in seven residues resist even enzymatic cleavage well, because proline locks the backbone rotation peptidases require. One practical cost of that composition: no aromatic residues means almost no absorbance at 280 nm, so the standard spectrophotometric quantification method does not work on it.

Deep dive: reading a two-literature evidence base

PubMed indexes roughly 135 Selank records against about 690 for its parent peptide tuftsin - an inversion worth noticing, since most designed analogues eventually outgrow the parent they replaced. Most of the tuftsin literature is immunological and predates Selank entirely, so it is not evidence about Selank. Within Selank's own record the split is the same one Semax shows: mechanistic work in internationally indexed journals, assessable directly; clinical work concentrated in Russian-language publications, indexed by translated title and often without accessible English full text. That is evidence which is hard to verify independently, which is not the same as evidence that is absent, and not the same as evidence that is established.

Research applications

▸Enkephalin and enkephalinase pathway research
▸GABAergic receptor expression studies in rodent models
▸BDNF expression research, including intranasal administration routes
▸Comparative work on proline-stabilised peptide design
▸Tuftsin and immunopeptide structure-activity research

Handling checklist

✓Store lyophilised material cold, dry and protected from light
✓No reducing agent needed — the sequence contains no cysteine
✓No methionine oxidation to expect; a +16 Da satellite warrants explanation
✓Do not rely on 280 nm absorbance — there are no aromatic residues
✓Introduce diluent gently against the vial wall; swirl rather than shake
✓Aliquot to avoid repeated freeze-thaw cycles

Common research-handling mistakes

Learnt from thousands of researcher orders across our UK labs.

✗ Describing Selank as an opioid or opioid agonist

Fix: Reported work describes inhibition of enkephalin-degrading enzymes, not receptor binding. It preserves endogenous enkephalins rather than supplying an agonist.

✗ Treating the benzodiazepine contrast as a safety claim

Fix: The mechanistic difference is real — expression-level rather than direct allosteric modulation — but it supports no comparative claim about safety or dependence.

✗ Citing tuftsin literature as evidence about Selank

Fix: Tuftsin has roughly five times more papers, most of them immunological and predating Selank. They are different compounds.

✗ Reading a BDNF expression change as a demonstrated outcome

Fix: The work measured expression in rat hippocampus. Expression is upstream of function and upstream again of any clinical claim.

✗ Treating Russian registration as equivalent to MHRA approval

Fix: Authorisations are jurisdictional and do not transfer. Selank has never been assessed by the MHRA, EMA or FDA.

Continue researching

Peer-reviewed guides, comparators and matched reference materials.

Frequently asked questions

Was the BDNF work done in humans?: No. It was conducted in rats, using intranasal administration.
Does raising BDNF expression prove an effect?: No. Expression is upstream of function, and a measurable change in a rodent brain region does not establish an outcome in an organism or a species.
Why is intranasal administration used?: It offers a route to the central nervous system that partially bypasses systemic circulation, which matters for peptides unlikely to cross the blood-brain barrier efficiently.

Primary sources & clinical trials

Peer-reviewed research and registered trials from PubMed, ClinicalTrials.gov, PubChem, FDA and NIH. All links open in a new tab and point to the primary source, so every claim can be verified at origin.

Written and reviewed by

Jack Muncaster · Founder, UK Peptides

Jack founded UK Peptides in Manchester after repeatedly receiving research compounds with missing or recycled paperwork. He is responsible for supplier selection, batch release decisions and the content published in this research library. Every article here is sourced to primary literature and every product page to a signed third-party certificate.

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