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Semax Research Guide — ACTH(4-10) Analogue and Neurotrophic Biology

What is Semax?

Semax is a synthetic heptapeptide (Met-Glu-His-Phe-Pro-Gly-Pro) derived from a fragment of adrenocorticotropic hormone (ACTH). It corresponds to the ACTH(4–10) sequence with an added C-terminal Pro-Gly-Pro tail that dramatically slows enzymatic breakdown, giving the peptide a far longer active window than the natural fragment. It is studied primarily as a neuroprotective and nootropic (cognition-modulating) research peptide, and is notable for producing central-nervous-system effects without the hormonal (cortisol-raising) activity of the parent ACTH molecule.

This guide summarises what Semax is, the neurobiology researchers use it to investigate, and the published literature — for laboratory research use only.

Origin: An ACTH(4–10) Analogue

ACTH is a 39-amino-acid hormone best known for stimulating cortisol release from the adrenal cortex. Decades of research established that its central (brain) effects — on learning, memory and attention — map to a short internal fragment, ACTH(4–10), which is functionally separable from the hormone’s corticotropic (cortisol-stimulating) region. Semax was developed at the Institute of Molecular Genetics in Russia to capture that neuroactive fragment as a stable, standalone peptide, adding Pro-Gly-Pro to resist the peptidases that would otherwise degrade ACTH(4–10) within minutes.

The result is a peptide that engages the brain’s ACTH-fragment signalling while leaving the adrenal axis largely untouched — the same “isolate one function of a larger molecule” design logic seen in other fragment peptides.

Mechanism

BDNF and NGF Modulation

The most studied mechanism of Semax is its effect on neurotrophins. Research reports that Semax rapidly increases the expression of brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF), along with their receptors, particularly in the hippocampus — a region central to learning and memory. BDNF and NGF support neuronal survival, synaptic plasticity and growth, which is the framework through which Semax’s cognitive and neuroprotective research effects are usually interpreted.

Monoaminergic and Melanocortin Effects

Semax also modulates monoamine systems (dopamine and serotonin) and interacts with the melanocortin system as an ACTH-fragment analogue. These actions are studied in the context of attention, motivation and mood regulation, and contribute to its classification as a nootropic research compound.

Why It Lacks Corticotropic (Cortisol) Activity

A defining feature is that Semax does not meaningfully stimulate cortisol release. The corticotropic activity of ACTH depends on regions of the molecule not present in the 4–10 fragment, so Semax delivers the central/neurotrophic signalling without the systemic stress-hormone response — the property that makes it a clean tool for isolating ACTH’s brain effects.

The Research Literature

Cognition and Attention

Semax has been investigated for effects on attention, memory consolidation and mental fatigue in both animal models and human research settings. The proposed basis is the combination of acute neurotrophin upregulation and monoaminergic modulation, which together are studied for their influence on cognitive performance under load.

Neuroprotection

A substantial share of the Semax literature concerns neuroprotection in models of cerebral ischaemia (restricted blood flow). Researchers have examined its capacity to limit neuronal damage and support recovery, again attributing effects largely to BDNF/NGF pathways and anti-inflammatory and antioxidant signalling. In Russia, Semax has been used clinically in stroke and cognitive contexts; in the UK and most other jurisdictions it is handled strictly as a research chemical.

Comparison: Semax vs Selank and Other Nootropic Peptides

Semax ACTH(4–10) analogue. Neurotrophic (BDNF/NGF) + monoaminergic; studied for cognition, attention and neuroprotection.
Selank Tuftsin analogue. Anxiolytic-leaning; modulates GABA/serotonin and immune signalling. See Selank 5mg and the Semax vs Selank comparison.
Both Short, stable peptide analogues of endogenous fragments, typically studied via intranasal administration. Overview: Nootropic Peptides research page.

The key distinction: Semax leans toward cognitive activation and neuroprotection via neurotrophins, whereas Selank leans toward anxiolytic and immunomodulatory effects — the two are frequently studied side by side.

Experimental Considerations

Semax is supplied as a lyophilised (freeze-dried) powder for reconstitution. As a peptide it is not orally stable and is typically administered intranasally in research protocols. Handling directly affects data quality:

  • Reconstitution — prepare with bacteriostatic water following standard technique; see the Peptide Reconstitution Guide for volume and concentration calculations.
  • Storage — keep lyophilised vials cold and protected from light; reconstituted solution is short-lived and should be refrigerated. See Peptide Storage best practices.
  • Purity — OLR’s Semax 5mg is supplied at ≥99% HPLC purity, UK-dispatched. Purity and correct reconstitution are the two biggest determinants of reproducible results.

Frequently Asked Questions

What is Semax derived from?
It is an analogue of the ACTH(4–10) fragment of adrenocorticotropic hormone, stabilised with a C-terminal Pro-Gly-Pro tail.

Does Semax raise cortisol?
No. The research literature reports it lacks the corticotropic activity of full ACTH — it engages the fragment’s central/neurotrophic signalling without stimulating the adrenal stress axis.

How is Semax administered in research?
As a peptide it is not orally stable; research protocols typically use intranasal administration of the reconstituted solution.

What is the difference between Semax and Selank?
Semax is studied mainly for cognition and neuroprotection (BDNF/NGF), while Selank is studied mainly for anxiolytic and immunomodulatory effects. See the comparison guide.

What is Semax used for?
In the UK it is supplied strictly as a laboratory research chemical for in-vitro and preclinical study. It is not for human or veterinary use.

Further Reading

For laboratory and scientific research use only. Not for human or veterinary use, consumption, or clinical application. Nothing on this page is medical advice or a therapeutic claim. All statements describe published research findings and mechanisms studied under laboratory conditions.