Semax: BDNF Upregulation and Neuroprotection Research
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# Semax: BDNF Upregulation and Neuroprotection Research
For Research Purposes Only — Not Intended for Human or Animal Consumption
Introduction
Semax (Met-Glu-His-Phe-Pro-Gly-Pro) is a synthetic heptapeptide derived from the N-terminal fragment of adrenocorticotropic hormone (ACTH 4-10). It was developed at the Institute of Molecular Genetics of the Russian Academy of Sciences and has been approved in Russia for the treatment of stroke, transient ischemic attack, and cognitive disorders. It is one of the most extensively studied nootropic peptides in the Russian scientific literature.
Structure and ACTH Relationship
ACTH (adrenocorticotropic hormone) is a 39-amino acid peptide produced by the pituitary gland that stimulates cortisol production from the adrenal cortex. The 4-10 fragment of ACTH (Met-Glu-His-Phe-Pro-Gly-Pro) retains cognitive-enhancing and neuroprotective properties of ACTH but lacks the adrenal-stimulating activity of the full-length hormone.
Semax adds a Pro-Gly-Pro sequence to the C-terminus of ACTH 4-10, which confers resistance to peptidase degradation and extends the biological half-life compared to the native ACTH fragment.
Mechanism of Action
BDNF upregulation: The best-characterized mechanism of Semax's cognitive effects is upregulation of Brain-Derived Neurotrophic Factor (BDNF) in the hippocampus and frontal cortex. Dolotov et al. (2006) demonstrated that intranasal Semax administration significantly increased BDNF mRNA and protein levels in rat hippocampus within hours of administration. BDNF promotes synaptic plasticity, hippocampal neurogenesis, and neuronal survival — mechanisms directly relevant to learning, memory, and neuroprotection.
Melanocortin receptor activation: Semax activates melanocortin receptors (MC4R and MC5R), which are expressed in the brain and mediate cognitive effects through cAMP/PKA signaling. MC4R activation in the hippocampus promotes long-term potentiation (LTP) — the cellular mechanism of memory formation.
Serotonin system modulation: Semax has been shown to increase serotonin turnover in limbic structures, which may contribute to mood-stabilizing and anxiolytic effects observed in some animal studies.
Dopaminergic effects: Some studies have reported effects of Semax on dopamine metabolism in the striatum, which may contribute to its effects on attention and motivation.
Neuroprotective Effects
Semax has been extensively studied in animal models of neurological injury, including:
Ischemic stroke: Semax administration in rat models of middle cerebral artery occlusion reduced infarct volume and improved neurological outcomes. The proposed mechanism involves BDNF-mediated neuroprotection and anti-inflammatory effects.
Traumatic brain injury: Semax reduced neuronal death and improved behavioral outcomes in rat TBI models.
Oxidative stress: Semax demonstrated antioxidant effects in several models, potentially through BDNF-mediated upregulation of antioxidant enzymes.
Clinical Evidence
Stroke treatment: Semax has been approved in Russia for acute ischemic stroke treatment. Clinical trials in Russian institutions have reported improved neurological outcomes with intranasal Semax administration in stroke patients, though these trials have not been replicated in Western clinical settings.
Cognitive disorders: Small clinical studies have reported cognitive improvements with Semax in patients with mild cognitive impairment and vascular dementia.
The clinical evidence is limited by the same factors as Selank — concentration in Russian institutions, small sample sizes, and lack of independent replication.
Pharmacokinetics
Like Selank, Semax is typically administered intranasally. The intranasal route provides direct access to the CNS via the olfactory pathway and avoids rapid degradation in systemic circulation. The half-life of Semax in systemic circulation is very short (minutes), but intranasal administration may provide sustained CNS exposure through the olfactory route.
References
- Dolotov, O.V., et al. (2006). Semax, an analogue of ACTH(4-10) with cognitive effects, regulates BDNF and trkB expression in the rat hippocampus. Brain Research, 1117(1), 54–60.
- Mjasoedov, N.F., et al. (1999). The study of Semax action on the processes of learning and memory in rats. Zhurnal Vysshei Nervnoi Deyatelnosti, 49(3), 420–428.
- Gusev, E.I., et al. (1997). Neuroprotective effects of Semax in patients with cerebral ischemia. Cerebrovascular Diseases, 7(Suppl 6), 34–39.