Overview
What is Selank?
Selank (also designated TP-7) is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. It was developed at the Institute of Molecular Genetics of the Russian Academy of Sciences — the same institution that produced Semax — and has been in active research use since the 1990s.
Its core is tuftsin (Thr-Lys-Pro-Arg), a naturally occurring tetrapeptide cleaved from the Fc region of immunoglobulin G in the spleen. Tuftsin is an endogenous immunomodulatory peptide with macrophage and NK cell activating properties. Selank uses this four-residue sequence as its foundation and extends it with a Pro-Gly-Pro tripeptide at the C-terminus — the same enzymatic stability strategy used in Semax's design — protecting it from rapid proteolytic degradation and extending its biological activity window.
While tuftsin's primary known role is immunomodulatory, Selank's research profile has developed primarily around anxiolytic and nootropic CNS effects, suggesting that the tuftsin sequence has neurological activity not fully appreciated in natural tuftsin alone — activity that becomes pharmacologically accessible with the added stability from the Pro-Gly-Pro extension.
| Property | Value |
|---|
| Full sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro (TKRPGP + C-terminal PGP) |
| Parent structure | Tuftsin (Thr-Lys-Pro-Arg) + Pro-Gly-Pro stabilizing extension |
| Molecular weight | ~751 Da |
| Administration routes | Intranasal (primary), subcutaneous |
| Primary research profile | Anxiolytic, anti-stress, nootropic |
| Origin | Institute of Molecular Genetics, Russian Academy of Sciences |
| Reconstitution | 2.5 mL BAC Water per 5mg → 2 mg/mL |
Structural Context
From Tuftsin to Selank
Tuftsin (Thr-Lys-Pro-Arg) is generated enzymatically from IgG in the spleen and liver. It is best known as an immune activator — it binds a receptor on monocytes and macrophages, stimulating phagocytosis, NK cell cytotoxicity, and cytokine production. The peptide was first isolated and characterized in the 1970s by Nishioka et al.
Despite its immunological characterization, tuftsin was recognized to have CNS activity as well — animal models suggested anxiolytic and behavioral effects, but native tuftsin degrades too rapidly in vivo to be a tractable research tool. Its half-life in plasma is measured in minutes due to activity by angiotensin-converting enzyme and other peptidases.
Adding Pro-Gly-Pro at the C-terminus solves this problem. Proline at the termini creates steric hindrance that slows exopeptidase cleavage, dramatically extending the compound's activity. The resulting heptapeptide — Selank — retains tuftsin's receptor-binding capability while being stable enough for meaningful pharmacological research.
Design Parallel · Semax vs Selank
Both Semax and Selank use the
Pro-Gly-Pro stabilization strategy: take a short, biologically active peptide that degrades too fast to study effectively, add a proline-terminated extension, and produce a research-viable compound. Semax's core is ACTH 4-7 (a hormonal fragment); Selank's core is tuftsin (an immune fragment). Both acquire CNS-accessible, neurologically active profiles after stabilization — suggesting the Pro-Gly-Pro group may contribute its own CNS activity, not just passive stability.
Mechanism of Action
How Selank Works
Selank's mechanism is not fully resolved — it operates across multiple systems simultaneously, which is typical of structurally simple peptides that interact with multiple receptor classes. The most studied pathways are:
GABAergic System Modulation
The most researched aspect of Selank's mechanism is its interaction with the GABAergic system. Research has documented changes in GABA-A receptor subunit expression in animal models following Selank administration — specifically upregulation of certain alpha subunits associated with anxiolytic tone. Crucially, this appears to occur via indirect mechanisms rather than direct GABA-A receptor binding at the benzodiazepine site, which is the basis for distinguishing Selank from classical benzodiazepine anxiolytics in research design.
BDNF Upregulation
Selank has been associated with BDNF (brain-derived neurotrophic factor) upregulation in animal models, though the effect is generally reported as less pronounced than Semax's BDNF response. BDNF supports neuronal survival and synaptic plasticity. The shared BDNF-modulating property between Selank and Semax — despite their different structural origins — suggests a convergent downstream effect via different upstream pathways, an area of active mechanistic investigation.
Serotonin Metabolism
Research from the Institute of Molecular Genetics has documented changes in serotonin catabolism in animal models treated with Selank — specifically altered activity of monoamine oxidase (MAO) on serotonin. Since serotonin tone is deeply connected to anxiety, mood, and stress responses, this interaction provides a second mechanistic axis for Selank's anxiolytic profile, distinct from the GABAergic pathway.
Enkephalin System
Some research has implicated the enkephalinase system in Selank's effects. Enkephalins are endogenous opioid peptides that modulate pain, stress, and mood. Selank has been proposed to inhibit enzymes that degrade enkephalins (notably leu-enkephalin), effectively prolonging the activity of endogenous opioid signaling in stress-reduction pathways. This mechanism would complement the GABAergic and serotonergic effects.
Immunomodulatory Activity (Tuftsin Heritage)
Selank retains the tuftsin immunomodulatory core sequence and has been shown in some studies to modulate cytokine production (IL-6, TNF-α) and interferon expression. The immunological dimension of Selank research is less prominent than its CNS profile, but the shared ancestry with tuftsin means immune function effects are an active research area, particularly in the context of stress-immune axis interactions.
Mechanistic Comparison
Selank vs Benzodiazepines as an Anxiolytic Research Model
Benzodiazepines produce anxiolytic effects by acting as positive allosteric modulators (PAMs) of GABA-A receptors. They bind a specific site at the interface of alpha and gamma subunits on the GABA-A receptor complex, enhancing the receptor's sensitivity to GABA — increasing chloride ion conductance and hyperpolarizing the neuron. This direct, acute mechanism produces rapid, robust anxiolytic effects but also tolerance, dependence, and sedation with repeated exposure.
Selank's proposed mechanism is fundamentally different: rather than acutely potentiating the GABA-A receptor, it appears to influence GABA-A receptor subunit composition over time — upregulating subunit expression that shifts the receptor's baseline state toward reduced anxiety tone. This is a slower, more epigenetic-type mechanism that operates through gene expression rather than receptor occupancy.
This distinction makes Selank of significant research interest as a model for studying anxiolysis without direct GABA-A PAM activity — specifically, whether meaningful anxiolytic effects can be achieved through indirect GABAergic mechanisms, and whether such mechanisms produce the dependence and withdrawal profiles associated with direct benzodiazepine-site binding.
| Feature | Benzodiazepines | Selank |
|---|
| Receptor action | Direct GABA-A PAM (BZD site binding) | Indirect GABAergic modulation (subunit expression) |
| Onset | Rapid (minutes) | Slower (subunit expression changes) |
| GABA-A effect | Acute potentiation of Cl⁻ conductance | Baseline receptor composition shift |
| Tolerance mechanism | BZD-site downregulation, subunit changes | Less studied; proposed to be lower |
| Serotonin effect | Minimal | MAO modulation, altered 5-HT catabolism |
| BDNF effect | Minimal | Upregulation documented in animal models |
| Sedation profile | Significant at anxiolytic doses | Less sedation observed in animal models |
Comparison
Selank vs Semax
Selank and Semax are the two flagship Russian nootropic research peptides, and they are frequently discussed together because they share a design strategy (Pro-Gly-Pro extension), a research institution, and intranasal compatibility. But they are distinct compounds with different primary mechanisms.
| Feature | Selank | Semax |
|---|
| Structural origin | Tuftsin (immune tetrapeptide) + PGP | ACTH 4–7 (pituitary fragment) + PGP |
| Primary mechanism | GABAergic modulation, serotonin, enkephalins | BDNF upregulation, dopamine, ACh systems |
| Primary research profile | Anxiolytic, anti-stress, calming | Cognitive enhancement, neuroprotection, activating |
| BDNF effect | Moderate upregulation | Strong, consistent upregulation |
| GABA interaction | Primary mechanism | Not a primary mechanism |
| Serotonin interaction | MAO modulation | Serotonin system (secondary) |
| Intranasal compatibility | Yes | Yes |
| Ischemia / stroke models | Less studied | Significant data |
| Typical research combination | Often co-studied: stress-cognition interface, anxiety + cognitive performance |
Research Context
Research Applications
Anxiety & Stress Models
Selank has shown anxiolytic effects in animal models using classical paradigms including open-field, elevated plus maze, and conflict test paradigms. Effects are generally dose-dependent and observed in both acute and repeated-administration models. Research interest is particularly focused on stress-induced anxiety models and whether effects are distinguishable from benzodiazepine-type compounds by their mechanism fingerprint.
Stress-Cognition Interface
Chronic stress degrades cognitive performance through mechanisms including HPA axis dysregulation and glucocorticoid-mediated hippocampal damage. Selank's combined anxiolytic (reduce stress load) and BDNF-modulating (support hippocampal neuroplasticity) properties make it a useful research tool for studying whether reducing anxiety tone can protect or restore cognitive function in stress models.
Non-Benzodiazepine Anxiolytic Mechanism Research
A major area of pharmacological interest is identifying anxiolytic mechanisms that don't share benzodiazepine limitations (tolerance, sedation, dependence). Selank serves as a well-characterized model compound for this research area — its anxiolytic profile without direct GABA-A PAM activity makes it a useful comparator and mechanistic probe.
Immunomodulatory Research
Selank inherits tuftsin's immunomodulatory properties and has been studied for effects on cytokine profiles, NK cell function, and interferon expression. This positions it at the intersection of neuroimmunology research — particularly relevant given growing evidence that the stress response and immune function are tightly linked via the HPA axis and vagal pathways.
Reconstitution
Reconstitution Protocol
Selank 5mg ships as lyophilized powder. Add 2.5 mL Bacteriostatic Water for a working concentration of 2 mg/mL. Inject BAC water slowly down the vial wall, swirl gently — do not shake. Solution should be clear and colorless. Refrigerate at 2–8°C after reconstitution. Stable for 28–42 days.
For intranasal research protocols, the 2 mg/mL stock is typically diluted further with sterile saline before loading into a nasal spray atomizer. The appropriate dilution depends on the target dose per spray volume — a common research approach uses 0.1–0.5 mg/mL concentrations for intranasal delivery.
FAQ
Common Questions
What is Selank?
Selank is a synthetic heptapeptide (Thr-Lys-Pro-Arg-Pro-Gly-Pro) that is an analogue of tuftsin, a naturally occurring immunomodulatory tetrapeptide from IgG. The added Pro-Gly-Pro extension stabilizes it against enzymatic degradation. It was developed in Russia and studied primarily for anxiolytic and nootropic properties through GABAergic modulation, BDNF upregulation, and serotonin system interactions.
How does Selank differ from benzodiazepines?
Benzodiazepines bind directly to the GABA-A receptor benzodiazepine site, acutely potentiating chloride conductance. Selank modulates GABAergic activity through indirect mechanisms — changes in GABA-A receptor subunit expression rather than direct receptor occupancy. This mechanistic distinction makes Selank valuable for studying non-benzodiazepine anxiolytic mechanisms.
What is the difference between Selank and Semax?
Selank (tuftsin analogue) is primarily studied for anxiolytic effects via GABAergic and serotonergic modulation — it trends calming. Semax (ACTH 4-7 analogue) is primarily studied for cognitive enhancement, BDNF upregulation, and neuroprotection — it trends activating. They share Pro-Gly-Pro stabilization, intranasal compatibility, and BDNF-modulating activity, making them complementary research compounds.
What is tuftsin and how does it relate to Selank?
Tuftsin (Thr-Lys-Pro-Arg) is an endogenous immunomodulatory tetrapeptide cleaved from the Fc region of IgG in the spleen. It activates macrophages and NK cells. Selank uses tuftsin's four-residue sequence as its core and adds Pro-Gly-Pro at the C-terminus to resist enzymatic degradation, enabling its CNS activity to be studied pharmacologically.
How do I reconstitute Selank?
Add 2.5 mL Bacteriostatic Water to the 5mg vial (2 mg/mL). Inject down the vial wall and swirl gently. For intranasal research, dilute further with sterile saline before use. Refrigerate at 2–8°C. Stable 28–42 days.