Selank & Semax: Nootropic Peptides from Russian Neuroscience Research

Selank and Semax are two of the most extensively studied nootropic peptides, both originating from Russia’s Institute of Molecular Genetics of the Russian Academy of Sciences. Though they are often mentioned together and share some overlapping neurobiological effects, they come from fundamentally different parent molecules, target distinct primary pathways, and produce different cognitive-behavioral profiles. Selank, derived from the immunomodulatory peptide tuftsin, operates primarily as an anxiolytic with secondary nootropic effects. Semax, derived from adrenocorticotropic hormone (ACTH), operates primarily as a nootropic with secondary neuroprotective effects.

This guide covers both Selank and Semax in detail — their molecular origins, individual mechanisms, published neuroscience data, and a head-to-head comparison to help researchers select the appropriate compound for their specific research question. We also discuss how they relate to other nootropic peptides in the Apex Laboratory catalog.

Selank: The Tuftsin-Derived Anxiolytic Peptide

Molecular Identity

Selank is a synthetic heptapeptide created by extending the naturally occurring tetrapeptide tuftsin (Thr-Lys-Pro-Arg) with a Pro-Gly-Pro C-terminal stabilizing sequence. Tuftsin is an endogenous immunomodulatory peptide fragment of immunoglobulin G (IgG) that is cleaved from the Fc region by splenic enzymes. By adding the PGP tripeptide extension, researchers at the Institute of Molecular Genetics created a metabolically stable version of tuftsin with enhanced CNS activity.

• Full Name: Selank (Thr-Lys-Pro-Arg-Pro-Gly-Pro)
• CAS Registry Number: 129954-34-3
• Molecular Weight: 751.88 g/mol
• Amino Acid Count: 7 residues (heptapeptide)
• Parent Molecule: Tuftsin (endogenous immunomodulatory tetrapeptide)
• Primary Activity: Anxiolytic with nootropic properties
• Regulatory Status: Approved in Russia as an anxiolytic medication

Mechanism of Action

Selank’s anxiolytic and nootropic effects are mediated through several documented mechanisms. Published research demonstrates modulation of the GABAergic system, including allosteric modulation of GABA-A receptors that produces anxiolytic effects without the sedation, tolerance, or dependence associated with benzodiazepine-class GABA modulators. This non-sedating anxiolytic profile is one of Selank’s most studied characteristics.

Additionally, published data documents Selank’s effects on brain-derived neurotrophic factor (BDNF) expression. BDNF is a key neurotrophin involved in synaptic plasticity, memory consolidation, and neuronal survival. Selank has been reported to increase BDNF mRNA expression in the hippocampus — a finding with implications for both anxiolytic and memory-enhancing effects, since hippocampal BDNF is critical for both emotional processing and spatial/declarative memory formation.

Selank also modulates monoamine neurotransmitter systems. Published research reports stabilization of serotonin metabolism and modulation of dopamine and norepinephrine turnover in key brain regions. This monoamine modulation may contribute to both the anxiolytic effects (serotonin) and the cognitive-enhancing effects (dopamine/norepinephrine) documented in behavioral studies.

Published Research Highlights

Clinical studies in Russia led to Selank’s approval as an anxiolytic medication, based on published data from trials comparing it to benzodiazepine anxiolytics. Key findings included comparable anxiolytic efficacy without sedation, cognitive impairment, or withdrawal effects. Additional published studies have documented improvements in attention, short-term memory, and cognitive flexibility in healthy subjects, as well as immunomodulatory effects consistent with its tuftsin heritage — including modulation of cytokine profiles and immune cell activity.

Semax: The ACTH-Derived Nootropic Peptide

Molecular Identity

Semax is a synthetic heptapeptide derived from the 4-10 fragment of adrenocorticotropic hormone (ACTH), with the same Pro-Gly-Pro C-terminal stabilizing extension used in Selank. While ACTH is known primarily for stimulating cortisol release from the adrenal cortex, the 4-10 fragment retains neurotropic activity without adrenocortical stimulation — meaning Semax provides the cognitive-enhancing effects of ACTH-related signaling without elevating cortisol.

• Full Name: Semax (Met-Glu-His-Phe-Pro-Gly-Pro)
• CAS Registry Number: 80714-61-0
• Molecular Weight: 813.93 g/mol
• Amino Acid Count: 7 residues (heptapeptide)
• Parent Molecule: ACTH (4-10) fragment of adrenocorticotropic hormone
• Primary Activity: Nootropic with neuroprotective properties
• Regulatory Status: Approved in Russia as a nootropic and neuroprotective agent

Mechanism of Action

Semax’s nootropic mechanism involves multiple complementary pathways. Published research documents potent BDNF upregulation — even more robust than Selank’s — with increased BDNF protein levels in the hippocampus, cortex, and basal forebrain regions critical for learning and memory. Semax also upregulates nerve growth factor (NGF) and neurotrophin-3 (NT-3), creating a broad neurotrophic support profile. Published data from Agapova et al. (2007) documented these neurotrophic effects in detail.

Semax modulates dopaminergic and serotoninergic neurotransmission in attention-related brain circuits. Published studies document enhanced dopamine turnover in the prefrontal cortex and striatum, with corresponding improvements in attention, working memory, and executive function in behavioral testing. This dopaminergic modulation without direct receptor agonism distinguishes Semax from stimulant-class nootropic compounds.

Published neuroprotective data demonstrates Semax’s ability to reduce oxidative stress markers, modulate inflammatory cytokine profiles in neural tissue, and promote neuronal survival under ischemic conditions. These neuroprotective properties have led to investigation of Semax in stroke and neurodegenerative disease research models in Russian clinical studies.

Published Research Highlights

Semax is approved in Russia for two clinical indications: cognitive enhancement (nootropic) and neuroprotection following cerebrovascular events. Published clinical data supports improvements in attention, memory consolidation, information processing speed, and cognitive recovery. Additional published preclinical data documents neuroprotective effects in ischemia models, neurodegenerative disease models, and oxidative stress models, with documented reductions in infarct volume and improved neurological outcome scores.

Selank vs Semax: Head-to-Head Comparison

The following comparison summarizes the key differences to help researchers select the appropriate compound:

• Parent molecule: Selank derives from tuftsin (immunomodulatory IgG fragment). Semax derives from ACTH 4-10 (neurotropic ACTH fragment).
• Primary activity: Selank is primarily anxiolytic with secondary nootropic effects. Semax is primarily nootropic with secondary neuroprotective effects.
• Anxiolytic potency: Selank demonstrates stronger anxiolytic effects (GABA modulation, serotonin stabilization). Semax has mild anxiolytic activity but is not primarily an anxiolytic.
• Cognitive enhancement: Both enhance cognition, but Semax shows stronger effects on attention, working memory, and processing speed (dopamine-mediated). Selank shows stronger effects on emotional regulation and stress-impaired cognition (GABA/serotonin-mediated).
• BDNF modulation: Both upregulate BDNF. Semax produces more robust BDNF increases across more brain regions. Selank’s BDNF effects are primarily hippocampal.
• Immunomodulation: Selank has documented immunomodulatory properties (consistent with tuftsin heritage). Semax does not have significant immune effects.
• Neuroprotection: Semax has the stronger neuroprotective profile, with published data in ischemia and neurodegeneration models. Selank has antioxidant properties but less robust neuroprotective data.
• Sedation: Neither compound produces sedation — both maintain clean cognitive profiles without drowsiness.
• Cortisol effects: Neither compound elevates cortisol, despite Semax’s ACTH origin. The 4-10 fragment lacks the adrenocortical-stimulating domains of full-length ACTH.

Choosing Between Selank and Semax for Your Research

Use Selank when your research focuses on anxiety-related behaviors, stress-impaired cognition, GABAergic modulation, or neuroimmune interactions. Use Semax when your research focuses on cognitive enhancement, attention, neuroprotection, or neurotrophic factor modulation. For research examining both anxiolytic and nootropic endpoints simultaneously, some protocols study both compounds in parallel groups.

Related Nootropic Peptides in the Apex Laboratory Catalog

Selank and Semax are part of a broader family of nootropic research compounds available from Apex Laboratory. Brief overviews of related compounds for context:

• Adamax (N-Acetyl Semax Amidate) — a modified Semax derivative with an acetyl group and amide modification that enhances CNS penetration and metabolic stability. Stronger neurotropic activity per dose than standard Semax in published data.
• Dihexa — a small molecule HGF/c-Met pathway agonist with picomolar-range potency for neuroplasticity promotion. Entirely different mechanism from Selank/Semax. Targets synaptogenesis and dendritic spine formation.
• PE-22-28 — a peptide derived from spadin (sortilin propeptide) that antagonizes TREK-1 potassium channels for antidepressant and cognitive effects. A newer compound with a growing published dataset.
• Cerebrolysin — a porcine brain-derived peptide preparation containing multiple neurotrophic factors. Used in clinical neurology research in Europe and Asia for neurodegenerative and post-stroke applications.
• Pinealon — a Khavinson bioregulatory tripeptide (Glu-Asp-Arg) targeting the central nervous system, particularly pineal and cortical tissue. Part of the same Russian bioregulatory peptide program as Epithalon.
• DSIP (Delta Sleep-Inducing Peptide) — a nonapeptide involved in sleep architecture modulation and stress response regulation, studied for its effects on delta wave sleep induction.

Storage, Handling, and Reconstitution (Both Compounds)

Lyophilized Storage

Store both Selank and Semax at -20°C. Both are small heptapeptides (~750-815 g/mol) with excellent lyophilized stability for 18-24+ months. See our Peptide Storage Guide.

Reconstitution

Both dissolve instantly in bacteriostatic water. For 5 mg vials, adding 2.5 mL produces 2 mg/mL (2,000 mcg/mL). Use our reconstitution calculator or follow our reconstitution protocol.

After Reconstitution

Store at 2-8°C, use within 21 days. Both compounds have good solution stability. Aliquot for -20°C frozen storage.

Frequently Asked Questions

What is the difference between Selank and Semax?

Selank derives from tuftsin (an immunomodulatory peptide) and is primarily anxiolytic with secondary nootropic effects — it calms without sedating. Semax derives from ACTH 4-10 (a neurotropic hormone fragment) and is primarily nootropic with secondary neuroprotective effects — it enhances cognition and attention. Both modulate BDNF but through different mechanisms and in different brain regions.

Do Selank or Semax cause sedation?

No. Neither compound produces sedation. Selank’s anxiolytic mechanism (GABA modulation) achieves anxiety reduction without the drowsiness or cognitive impairment associated with benzodiazepines. Semax’s nootropic mechanism enhances alertness and attention. Both maintain clean cognitive profiles.

Does Semax raise cortisol levels?

No. Despite being derived from ACTH, Semax corresponds to the 4-10 fragment which retains neurotropic activity but lacks the 1-24 sequence required for adrenocortical stimulation. Published data confirms that Semax does not elevate cortisol, ACTH, or aldosterone levels.

Are Selank and Semax approved for medical use anywhere?

Both are approved as medications in Russia — Selank as an anxiolytic and Semax as a nootropic/neuroprotective agent. Neither is approved by the FDA or European regulatory agencies. All Selank and Semax sold by Apex Laboratory is intended strictly for in-vitro laboratory research.

What is Adamax and how does it relate to Semax?

Adamax (N-Acetyl Semax Amidate) is a chemically modified derivative of Semax with an N-terminal acetyl group and C-terminal amide modification. These modifications enhance its metabolic stability and CNS penetration, producing stronger neurotrophic effects per dose than standard Semax. Think of Adamax as an optimized version of Semax with improved pharmacokinetic properties.

Continue Your Research

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• BPC-157 Peptide: Mechanism, Research Applications & Studies
• Peptide Storage Guide: Temperature, Stability & Shelf Life

Research Use Disclaimer

This article is provided for educational and research reference purposes only. Selank, Semax, and all products sold by Apex Laboratory are intended exclusively for in-vitro laboratory research use and are not for human consumption. While both compounds are approved medications in Russia, they are classified as research chemicals in other jurisdictions. Researchers should consult the primary published neuroscience literature for complete data.