Semax: Neuroprotection, BDNF Upregulation, and Cognitive Research

Research Disclaimer: Semax is sold exclusively for in-vitro and laboratory research use. Not approved for human therapeutic use in most countries. This content does not constitute medical advice.

Semax (Met-Glu-His-Phe-Pro-Gly-Pro) is a heptapeptide derived from the ACTH4-10 sequence — the melanocortin-stimulating fragment of adrenocorticotropic hormone — with Pro-Gly-Pro added to the C-terminus to improve stability and CNS penetration. Developed in Russia in the 1980s and registered in Russia as a medical drug for stroke and ischemia treatment, Semax is one of the most studied neuroprotective peptides in neuroscience research.

Semax's primary research-relevant mechanisms include upregulation of BDNF (brain-derived neurotrophic factor), NGF (nerve growth factor), and their receptors, modulation of dopaminergic and serotonergic signaling, and direct neuroprotection against ischemic injury.

Table of Contents#

1. Semax Structure and Origin
2. ACTH4-10 Pharmacology: The Parent Fragment
3. BDNF Upregulation: The Primary Neuroprotective Mechanism
4. NGF and Neurotrophin Receptor Upregulation
5. Anti-Ischemic and Stroke Research
6. Dopaminergic and Serotonergic Modulation
7. Cognitive Research
8. Administration Routes
9. Research Protocols
10. Frequently Asked Questions
11. Key References

Semax Structure and Origin#

Full name: Methionyl-glutamyl-histidyl-phenylalanyl-prolyl-glycyl-proline
Sequence: Met-Glu-His-Phe-Pro-Gly-Pro (MEHFPGP)
Molecular weight: 813.9 Da

Structure relative to ACTH:

• ACTH is a 39-amino-acid pituitary hormone
• ACTH4-10 (Glu-His-Phe-Arg-Trp-Gly-Lys-Pro) is the minimal sequence retaining melanocortin receptor binding and CNS effects
• Semax = Met-ACTH4-7 (Glu-His-Phe-Pro) + Pro-Gly-Pro (C-terminal stability extension)
• Arg and Trp (positions 8–9 of ACTH4-10) are absent → Semax has reduced melanocortin receptor binding

The Pro-Gly-Pro C-terminal tripeptide:

1. Protects against C-terminal peptidase degradation
2. Has independent CNS effects via the Pro-Gly-Pro regulatory peptide (endogenous, produced by collagen breakdown → neuroprotective)

Production#

Semax was developed at the Institute of Molecular Genetics (Russian Academy of Sciences). Available in Russia as a pharmaceutical (0.1% and 1% nasal drops, branded "Semax"). Research-grade Semax is available as a lyophilized peptide for reconstitution.

ACTH4-10 Pharmacology: The Parent Fragment#

ACTH4-10 (the parent of Semax's core sequence) has been studied as a cognition-enhancing, attention-modulating peptide since the 1970s. Key properties:

• Does not stimulate cortisol: ACTH4-10 lacks the C-terminal portion required for adrenocortical steroidogenesis. It has cognitive/behavioral effects without corticosteroid effects.
• Modulates attention and memory: clinical studies with ACTH4-10 showed improved attention span, visual perception, and learning rate
• Short half-life: ACTH4-10 is rapidly degraded by plasma peptidases; Semax's modifications improve stability

Semax retains the cognitive-enhancing core of ACTH4-10 but adds the stability improvements and the Pro-Gly-Pro neurotrophic component.

BDNF Upregulation: The Primary Neuroprotective Mechanism#

What is BDNF?#

Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophin family that:

• Promotes neuronal survival, growth, and differentiation
• Supports synaptic plasticity (LTP — long-term potentiation, the cellular basis of memory)
• Protects neurons against ischemic and oxidative injury
• Regulates dopaminergic, serotonergic, and glutamatergic signaling
• Declines in Alzheimer's disease, depression, and aging

BDNF acts through TrkB (tropomyosin receptor kinase B) receptors → PI3K/Akt (survival) and MAPK/ERK (plasticity, differentiation) pathways.

Semax → BDNF elevation#

Semax is one of the most potent peptide BDNF inducers studied:

Intravenous and intranasal Semax in rats (Shadrina et al. 2001 and subsequent):

• Significant elevation of BDNF mRNA in hippocampus and cortex within 1–4 hours of administration
• BDNF protein elevation: 20–60% above baseline in hippocampus at 4–24h
• Effect persists 24–48 hours after single administration
• Repeated dosing produces sustained BDNF elevation without apparent tolerance

The mechanism of Semax-driven BDNF induction is not fully characterized but involves:

• Direct effects on neurons (possibly melanocortin receptor-independent)
• Indirect effects via dopaminergic and serotonergic tone changes
• Pro-Gly-Pro component contributes independently

Why BDNF elevation matters#

BDNF elevation → enhanced LTP → improved learning and memory consolidation. BDNF elevation also → neuronal resistance to ischemia, reduced apoptosis after glutamate excitotoxicity, and protection against dopaminergic neuron loss.

This mechanism explains Semax's documented effects in stroke research (see below) and cognitive research.

NGF and Neurotrophin Receptor Upregulation#

In addition to BDNF, Semax also elevates:

• NGF (nerve growth factor): 1.5–2.5× increase in cortex and hippocampus after intranasal Semax in rats
• TrkA (NGF receptor): upregulated in parallel with NGF
• TrkB (BDNF receptor): upregulated with BDNF → the receptor and its ligand both rise → enhanced signaling amplitude

The co-upregulation of neurotrophins AND their receptors produces a larger net biological response than ligand elevation alone would suggest.

NGF is particularly important for:

• Cholinergic neuron survival (basal forebrain cholinergic neurons require NGF for maintenance)
• Peripheral nerve regeneration
• Nociceptive signaling (pain research)

Anti-Ischemic and Stroke Research#

Semax is registered in Russia specifically for ischemic stroke treatment (as an adjunct to standard care), based on preclinical and some clinical evidence.

Preclinical data#

In rodent middle cerebral artery occlusion (MCAO) models:

• Intranasal Semax (50–100 µg/kg) administered within 6h of MCAO onset
• Infarct volume reduction: 30–50% smaller ischemic core vs. vehicle
• Neurological score: improved motor and sensory deficits at 24–72h
• Mechanisms: BDNF elevation → neurotrophic support of peri-infarct tissue; reduced expression of pro-inflammatory cytokines (IL-1β, TNF-α) in penumbra; reduced caspase-3 activation (anti-apoptotic)

Transcriptomic data#

Published microarray/RNA-seq studies (Moscow groups, 2010s):

• Semax in ischemia model → upregulates 150+ neuroprotective genes including BDNF, VEGF, SIRT1 (survival), heat shock proteins
• Downregulates pro-apoptotic and pro-inflammatory gene networks
• Time course: gene expression changes visible within 3–6 hours of administration

Clinical data (Russian studies)#

Small clinical trials in Russia (not double-blind placebo-controlled per Western standards):

• Patients with acute ischemic stroke + Semax nasal drops (0.1%): improved neurological outcomes vs. standard care alone
• Methodological limitations preclude definitive conclusions; these data support continued mechanistic and larger-trial research

Dopaminergic and Serotonergic Modulation#

Beyond neurotrophins, Semax modulates monoaminergic systems:

Dopamine#

• Semax increases dopamine release in the striatum and frontal cortex (measured by microdialysis in rats)
• Dopamine D1 receptor upregulation in some brain regions
• This dopaminergic effect contributes to attention-enhancing properties (dopamine mediates working memory and attention in prefrontal cortex)

Serotonin#

• Semax elevates 5-HT (serotonin) in cortex and hippocampus
• 5-HT1A and 5-HT2A receptor expression changes after chronic Semax
• The serotonergic component may contribute to Semax's reported anxiolytic effects

Opioid system#

• Some evidence for interaction with the opioid system (modest affinity at mu-opioid receptor has been reported for ACTH4-10 analogs)
• Contribution to analgesic and cognitive effects

Cognitive Research#

Memory and learning (rodent models)#

Standard behavioral models used with Semax:

• Morris water maze: improved spatial learning and memory consolidation
• Passive avoidance: improved retention of learned fear response
• Novel object recognition: improved recognition memory

In these models, Semax (intranasal, 50–100 µg/kg):

• Reduces escape latency in Morris water maze by 20–40%
• Improves avoidance retention for 48–72h post-training
• Effects are blocked by TrkB antagonists → confirming BDNF/TrkB mediation

Attention (ADHD models)#

In spontaneously hypertensive rat (SHR) ADHD model:

• Semax normalizes attention deficits and hyperactivity
• This effect is likely mediated by dopaminergic normalization in prefrontal cortex

Alzheimer's disease models#

In amyloid-β-induced cognitive impairment models:

• Semax preserves cholinergic neuron density in the basal forebrain (NGF-dependent)
• Improves spatial memory retention
• Does not directly reduce amyloid burden in published studies

Administration Routes#

Intranasal (primary research route)#

Intranasal delivery bypasses the blood-brain barrier via the olfactory-trigeminal pathway:

• Drug follows the perineural space of cranial nerve I/V to the olfactory bulb → direct brain access
• Avoids systemic dilution and hepatic first-pass metabolism
• Standard research format: nasal drops or nasal spray

In vivo intranasal dosing for rodents:

• Volume: 2–5 µL per nostril
• Semax concentration: typically 0.1–1 mg/mL solution
• Dose: 50–200 µg/kg total

Subcutaneous (alternative)#

SC injection is used in some research protocols where intranasal delivery is less reproducible:

• Bioavailability to CNS lower than intranasal (peptide must cross BBB)
• Higher peripheral concentrations
• Standard dose: 100–500 µg/kg SC

Intraperitoneal / intravenous#

For acute pharmacological studies requiring precise dosing and rapid CNS exposure.

Research Protocols#

Neuroprotection protocol (ischemia model)#

Cognitive enhancement protocol#

Frequently Asked Questions#

Does Semax affect cortisol? No. The full ACTH sequence (particularly the C-terminal fragment) is required for adrenocortical stimulation. Semax's ACTH4-7 core lacks this activity. Multiple studies confirm no cortisol elevation from Semax at research doses.

How does Semax differ from Selank? Both are Russian nootropic peptides. Semax (ACTH analog, BDNF/NGF elevating) is more studied for neuroprotection and cognitive enhancement. Selank (tuftsin analog, anxiolytic/nootropic) primarily modulates GABA-A receptors and is more studied for anxiety. They can be combined in some research protocols.

Is Semax a melanocortin agonist? Weakly. Semax has some affinity at MC4R and MC5R but far less than full ACTH or alpha-MSH. The cognitive effects do not appear to require melanocortin receptor activation in published studies.

Key References#

1. Shadrina MI, et al. (2001). "Neurotrophic effects of Semax peptide." Bulletin of Experimental Biology and Medicine, 132(6):1175–1177.

2. Agapova TY, et al. (2007). "Effects of Semax and its C-terminal fragment Pro-Gly-Pro on the development of fear memory." Bulletin of Experimental Biology and Medicine, 144(5):611–613.

3. Kolomin T, et al. (2013). "The new generation of drugs based on the neuropeptide analog Semax." Journal of Neurological Disorders, 1(4):1–7.

4. Malinovskaya NA, et al. (2016). "Efficacy of cortexin and Semax in correction of cognitive impairments in animal models." Neuroscience and Behavioral Physiology, 46(2):168–175.

5. Tugai VA, et al. (1997). "Effects of Semax on the learning and memory in rats and mice." Eksperimental'naia i Klinicheskaia Farmakologiia, 60(3):36–38.

Research Use Only: Semax and all products referenced are sold exclusively for in-vitro research and laboratory use. Not for human consumption. JuicedPharma does not provide medical advice.

Published by JuicedPharma Research Team · September 2026 · Category: Research Protocols & Science