Leucine Enkephalin (Leu-Enkephalin) vs Selank
A neutral, side-by-side comparison of two nootropic & cognitive peptides — their mechanisms, dosing ranges, administration routes, side effects, and research evidence. For research and educational purposes only.
Leucine Enkephalin (Leu-Enkephalin)
One of the two primary endogenous enkephalins, alongside met-enkephalin. This pentapeptide (Tyr-Gly-Gly-Phe-Leu) acts primarily on δ-opioid receptors and secondarily on μ-opioid receptors. Research interests span pain modulation, neuroprotection, mood regulation, and immune system modulation. Extremely short half-life in vivo due to rapid enkephalinase degradation.
Full profileSelank
Selank is a synthetic heptapeptide derived from tuftsin, an endogenous immunomodulatory peptide. Developed in Russia by the Institute of Molecular Genetics, it has been studied extensively for anxiolytic, nootropic, and immunomodulatory effects. It is registered as a medication in Russia and Ukraine.
Full profile| Leucine Enkephalin (Leu-Enkephalin) | Selank | |
|---|---|---|
| Category | Nootropic & Cognitive | Nootropic & Cognitive |
| Also known as | Leu5-enkephalin, YGGFL, L-enkephalin, endogenous opioid pentapeptide | TP-7, Tuftsin analog |
| Evidence | Research-stage | Research-stage |
| Dosing range | 0.1mg–1mg mg, Intranasal or SC; extremely short half-life requires frequent dosing or continuous delivery | 250mcg–1000mcg mcg, 1–2x daily |
| Administration | Intranasal, Subcutaneous injection, Intraventricular (research only) | Intranasal (most common — direct CNS delivery), Subcutaneous injection |
| Key side effects | Tolerance development with repeated use (opioid receptor class effect), Mild euphoria (δ-opioid mediated), Nausea (at high doses), Constipation (opioid class effect at high doses) | Mild sedation at high doses, Nasal irritation (intranasal route), Generally very well-tolerated, No reported dependence or withdrawal |
| Cited sources | 2 references | 1 reference |
Key differences
- Administration: Leucine Enkephalin (Leu-Enkephalin) — Intranasal, Subcutaneous injection, Intraventricular (research only); Selank — Intranasal (most common — direct CNS delivery), Subcutaneous injection.
- Dosing units differ: Leucine Enkephalin (Leu-Enkephalin) is dosed in mg, Selank in mcg — they operate at different scales.
- Frequency: Leucine Enkephalin (Leu-Enkephalin) is typically Intranasal or SC; extremely short half-life requires frequent dosing or continuous delivery; Selank is 1–2x daily.
- Research depth: this profile cites 2 sources for Leucine Enkephalin (Leu-Enkephalin) vs 1 for Selank.
How each works
Leucine Enkephalin (Leu-Enkephalin)
Leu-enkephalin was one of the first endogenous opioid peptides characterized, following the discovery of opioid receptors in 1973. It preferentially activates δ-opioid receptors (DOR) over μ-opioid receptors (MOR), producing analgesia, modulation of GABA release, and reward pathway activation. Enkephalinase (neprilysin/NEP, CD10) cleaves the Gly-Phe bond within ~2 minutes IV, necessitating stable analogues or NEP inhibitors for research applications.
Selank
Selank modulates GABA-A receptors and influences BDNF expression, producing anxiolytic effects comparable to benzodiazepines without sedation or dependence. Russian clinical studies report improvements in generalized anxiety disorder, cognitive performance, and mood stability. It also appears to modulate T-helper cell ratios and interferon production.
This comparison aggregates public research and structured profile data for informational purposes only. It is not medical advice and does not recommend either compound for human use. Consult a qualified healthcare provider before considering any peptide.