Semax and BDNF: What the Nootropic Studies Measured and How Strong They Are

LynxLab · 24 October 2026 · 8 min read

What the rat BDNF experiments and the human EEG and attention studies on Semax measured, with the actual numbers, and an honest grading of the evidence.

Photo: MART PRODUCTION, Pexels

Search for Semax online and the word that follows it most often is "nootropic", usually next to a claim about BDNF. Both ideas trace back to a specific set of experiments in Moscow, most of them in rats, a few in people. This post sets out what those studies measured, what numbers they produced, and how far the data for semax can honestly be stretched.

Why Semax researchers chase BDNF

Brain-derived neurotrophic factor, BDNF, is a protein that neurons use to survive, grow connections and adjust the strength of synapses. It signals through a receptor called TrkB. Low BDNF has been reported in depression, in ageing and after stroke, so any compound that raises it in the brain draws attention.

The Moscow group's interest started with astrocyte cultures. Dolotov and colleagues at the Institute of Molecular Genetics found that Semax stimulated BDNF synthesis in astrocytes taken from rat basal forebrain, which prompted them to ask whether the same thing happened in a living animal (Dolotov et al., Journal of Neurochemistry, 2006).

That question produced the two papers that most Semax claims rest on. Both are from 2006, both are from the same laboratory, and both used rats.

The rat hippocampus data: a 1.4-fold rise

The first paper gave rats a single intranasal dose of Semax at 50 micrograms per kilogram and then measured the BDNF system in the hippocampus, the brain region most associated with memory. BDNF protein rose a maximum of 1.4-fold. Phosphorylation of its receptor TrkB rose 1.6-fold, and the messenger RNA for exon III BDNF and for TrkB rose 3-fold and 2-fold respectively (Dolotov et al., Brain Research, 2006).

The behavioural measure in the same study was a conditioned avoidance task. Semax-treated rats showed "a distinct increase in the number of conditioned avoidance reactions", and the authors proposed that the cognitive effects of the semax peptide work through the hippocampal BDNF/TrkB system.

The second 2006 paper looked at the basal forebrain and asked a sharper question: does Semax bind to anything? Tritium-labelled Semax bound to membranes from rat basal forebrain in a way that was time-dependent, specific and reversible. The dissociation constant was 2.4 nanomolar and the number of binding sites was 33.5 femtomoles per milligram of protein. Intranasal Semax at 50 and 250 micrograms per kilogram raised BDNF in the basal forebrain within 3 hours, but not in the cerebellum.

A binding site is not a receptor. The authors did not identify the protein Semax was binding to, and as of 2026 nobody has. The finding shows the peptide reaches the brain and does something specific there; it does not explain what.

The time-course study complicates the picture

A 2010 paper from the same institute followed BDNF and nerve growth factor, NGF, gene expression over time after Semax, at 20 minutes, 40 minutes, 90 minutes, 3 hours, 8 hours and 24 hours, in hippocampus, frontal cortex and retina. The result was not a clean rise.

At 20 minutes expression of both genes fell in the hippocampus and retina while rising in the frontal cortex. BDNF in the retina then rose significantly at 90 minutes. The authors called the pattern "multidirectional activation" (Shadrina et al., Journal of Molecular Neuroscience, 2010).

This matters for anyone quoting the 1.4-fold figure. The direction of the BDNF change depends on which region is sampled and when. A single number from one region at one time point is a snapshot, and the laboratories that produced it have said so. Marketing copy for semax in the UK quotes the fold-change far more often than the time course.

What the human EEG studies actually did

Human data on Semax cognition come from two small 1996 papers, both from Moscow. Koroleva and colleagues gave intranasal Semax to 9 healthy volunteers and distilled water to 6 controls, then recorded EEG. Semax produced "a boost of biopotential strength in all ranges but especially in that of the alpha-rhythm", with no pathological signs (Koroleva et al., Bulletin of Experimental Biology and Medicine, 1996).

The second paper, by Alexander Kaplan and Igor Ashmarin's group at Moscow State University, reported that Semax changed the EEG after short-term hyperventilation in a way the authors read as antihypoxic and "similar to those seen after administration of typical nootropic drugs". Doses were 0.25 to 1.0 mg intranasally, about 4 to 16 micrograms per kilogram, and the paper describes a 20 to 24 hour effect on "the work efficiency of operators" (Kaplan et al., Neuroscience Research Communications, 1996).

Neither paper reports a validated memory or attention test with a score. The word nootropic, used in the title of the Kaplan paper, is doing a lot of work. In 1996 it meant a drug that changed EEG in the same direction as piracetam; it did not mean a measured improvement in cognition. Laboratories buying semax for research should read those two abstracts before citing either.

The only patient cognition data comes from stroke

The one setting where Semax has been given to patients with outcome scores is stroke, covered in detail in the sibling post on the history and regulatory status of Semax. The 2018 study by Gusev and colleagues is relevant here because it is the only human BDNF measurement.

In 110 post-stroke patients, those who received two 10-day courses of Semax at 6000 mcg a day had higher plasma BDNF that "remained high during the whole study period", and higher BDNF correlated with faster improvement on the Barthel index (Gusev et al., Zhurnal Nevrologii i Psikhiatrii, 2018). Plasma BDNF is not brain BDNF, and the study was not blinded, but it is the one place where the rat finding and a human finding point the same way.

The transcriptome work: anti-inflammatory, not just neurotrophic

Since 2020 the Institute of Molecular Genetics has moved from single genes to whole-transcriptome sequencing. In a rat model of stroke, transient occlusion of the middle cerebral artery, Semax changed the expression of 394 genes by more than 1.5-fold at 24 hours compared with saline. It suppressed genes linked to inflammation and activated genes linked to neurotransmission, the mirror image of what the stroke itself did (Filippenkov et al., Genes, 2020).

A 2021 follow-up used quantitative PCR to check the inflammatory genes that RNA sequencing had struggled to measure. Semax produced a statistically significant fall in Il1a, Il1b, Il6, Ccl3 and Cxcl2 messenger RNA, cancelling the rise caused by ischaemia-reperfusion (Dergunova et al., Molekuliarnaia Biologiia, 2021).

The direction of travel in the research is clear. The group that spent the 2000s describing Semax as a BDNF booster now describes it as an anti-inflammatory peptide whose neuroprotective effect "may be due to its anti-inflammatory effects". Anyone who wants to buy semax for a neuroscience project should know that the mechanism story is still being rewritten by the people who started it.

How strong is the evidence, graded honestly

Taking the studies together, this is where the record stands in October 2026.

BDNF rise in rat brain after intranasal Semax: shown repeatedly, by one institute, with a complicated time course.
A specific binding site in rat basal forebrain: shown once, receptor unidentified.
Improved learning in rats: shown in avoidance tasks, by the same institute.
EEG changes in healthy humans: two 1996 papers, 9 volunteers in one, no placebo described.
Measured cognitive improvement in healthy humans with a validated test: not published.
Independent replication outside Russia: not published.

The German neuroscientist Joachim Engele co-authored the 2006 rat papers from Leipzig, so the work was not sealed inside one country. But the behavioural and human studies all share authors, funders and a city. For a compound in research use, the gap between "raises BDNF in a rat hippocampus" and "improves human memory" is the whole experiment, and it has not been run.

LynxLab stocks semax 10mg for research use at £24.99 a vial, tested to 99% purity, with the lab reports on the product page.

Frequently asked questions

Does Semax increase BDNF?

In rats, yes, by a reported 1.4-fold in hippocampal protein after a single 50 mcg/kg intranasal dose (Dolotov et al., 2006). In humans, the only data is plasma BDNF in 110 stroke patients in a 2018 unblinded study. There is no published measurement of brain BDNF in people.

Is Semax a proven nootropic?

No. The nootropic label comes from two 1996 Moscow EEG papers in small groups of volunteers, neither of which reported a validated cognitive test score. The rat learning data is consistent, but no placebo-controlled trial of Semax on human memory or attention has been published.

How does Semax get into the brain?

The research used intranasal administration in both rats and humans, and the 2006 Journal of Neurochemistry paper found BDNF rising in rat basal forebrain within 3 hours of nasal dosing but not in the cerebellum. Specific binding sites were measured, but the receptor has not been identified.

What is the latest Semax research about?

Since 2020 the Institute of Molecular Genetics in Moscow has used RNA sequencing in a rat stroke model, finding 394 genes changed at 24 hours and a strong anti-inflammatory signature. A 2021 paper confirmed falls in Il1a, Il1b and Il6 expression, shifting the proposed mechanism from neurotrophic towards anti-inflammatory.

Sources

Research use only

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