Semax vs Selank: A Neuropeptide Research Comparison
Quick verdict
Semax and Selank are both Russian-developed, Pro-Gly-Pro-stabilised neuropeptides studied together in cognitive research, but they target different systems: Semax (an ACTH(4–7) analogue) is studied for BDNF/NGF neurotrophic signalling and neuroprotection, while Selank (a tuftsin analogue) is studied for anxiolytic activity via GABAergic modulation. For research into neurotrophic factors, neuroprotection or cognition, Semax is the more direct tool; for research into anxiety-like behaviour and the GABA system, Selank is. Because the two systems are complementary, they are very commonly studied together — available as the cognitive research stack.
Overview: why these two are compared
Semax and Selank are the two best-known peptides from the Eastern European neuropeptide research tradition, and they are constantly compared because they share an origin story but split on mechanism. Both were created by taking a short natural peptide and adding a stabilising Pro-Gly-Pro tail. The difference is what the parent peptide does: Semax descends from a fragment of the stress hormone ACTH and is studied for building neural signalling (neurotrophins), while Selank descends from the immune peptide tuftsin and is studied for calming it (GABAergic, anxiolytic).
Origin and structure
Semax is the heptapeptide Met-Glu-His-Phe-Pro-Gly-Pro — the ACTH(4–7) fragment of adrenocorticotropic hormone extended with a Pro-Gly-Pro tail. Crucially it retains the neuro-regulatory signalling of ACTH without its hormonal (corticosteroid-releasing) activity. See the full Semax research overview.
Selank is the heptapeptide Thr-Lys-Pro-Arg-Pro-Gly-Pro — the immunomodulatory peptide tuftsin extended with the same stabilising Pro-Gly-Pro tail. Its tuftsin heritage is why Selank is studied for both behavioural and immune signalling. See the full Selank research overview.
Mechanism: neurotrophic vs GABAergic
Why it matters: mechanism is the clearest way to choose between these two, because it maps directly onto the research question — cognition and neuroprotection versus anxiety and stress.
Semax — BDNF/NGF and neuroprotection
The most studied property of Semax is its association with increased expression of brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) — the signalling proteins that govern neuron survival, growth and synaptic plasticity. It has also been examined in rodent models of cerebral ischaemia for neuroprotective gene activation. Semax is therefore the tool for research into neurotrophic signalling, neuroprotection and cognition.
Selank — GABAergic anxiolytic modulation
Selank’s defining property is modulation of the GABAergic system — the brain’s principal inhibitory pathway — producing anxiolytic-like effects in rodent models without binding the benzodiazepine site and without the sedation typical of classical anxiolytics. It is also associated with BDNF expression, but its centre of gravity is anxiety and stress research.
The verdict on mechanism
They are complementary rather than competing: Semax leans neurotrophic and pro-cognitive, Selank leans inhibitory and anxiolytic. A research model exploring both cognition and stress is the classic case for studying them together.
Side-by-side comparison
| Property | Semax | Selank |
|---|---|---|
| Parent peptide | ACTH(4–7) fragment | Tuftsin |
| Sequence | Met-Glu-His-Phe-Pro-Gly-Pro | Thr-Lys-Pro-Arg-Pro-Gly-Pro |
| Key pathway | BDNF / NGF neurotrophic | GABAergic (anxiolytic) |
| Primary research focus | Cognition, neuroprotection, neurotrophins | Anxiety, stress, GABA modulation |
| Sedation in models | Not associated | Anxiolytic without sedation |
| CAS number | 80714-61-0 | 129954-34-3 |
Key research findings
Representative peer-reviewed preclinical studies for each compound, summarised for scientific reference only.
Reported a rapid, region-specific increase in BDNF protein following intranasal Semax — direct evidence linking it to neurotrophic signalling.
PMID: 16635254
Mapped region-specific NGF/BDNF transcription dynamics following Semax across three brain regions.
PMID: 19662538
Reported anxiolytic effects comparable to diazepam in rodent models, but without the motor impairment or sedation of classical anxiolytics.
PMID: 19916388
Linked Selank’s behavioural effects to BDNF regulation — a point of mechanistic overlap with Semax.
PMID: 31625062
Why they are studied together
Because Semax and Selank act on different systems — neurotrophic versus GABAergic — researchers investigating cognition and stress together frequently study them in parallel, and they share the same intranasal-friendly, Pro-Gly-Pro-stabilised design. Velox Peptides supplies the pairing as the cognitive research stack, and both sit within the neuropeptide research category.
Which to study for which research question
Reach for Semax when the research question centres on neurotrophic factors (BDNF/NGF), neuroprotection in ischaemia models, or cognition, attention and learning.
Reach for Selank when the research question centres on anxiety-like behaviour, stress-response modulation, or the GABAergic system — particularly where a non-sedating, non-benzodiazepine mechanism is wanted.
Study both together when the model spans cognition and stress at once — the rationale behind the cognitive research stack.
References & further reading
- Dolotov OV et al. “Semax... increases levels of brain-derived neurotrophic factor protein in rat basal forebrain.” 2006. PMID: 16635254
- Shadrina M et al. “NGF and BDNF gene expression in rat hippocampus, frontal cortex and retina under Semax action.” 2009. PMID: 19662538
- Seredenin SB, Kozlovskaya MM et al. Selank anxiolytic activity in rodent anxiety models. PMID: 19916388
- Kozlovskaya et al. “Selank protects against ethanol-induced memory impairment by regulating BDNF content in the hippocampus and prefrontal cortex in rats.” 2019. PMID: 31625062
Summaries are paraphrased from the peer-reviewed preclinical literature. For full source citations, email veloxpeps@gmail.com.
