Leucine Enkephalin (Leu-Enkephalin) vs N-Acetyl 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 profileN-Acetyl Selank
Acetylated variant of Selank with enhanced stability and bioavailability. The N-acetyl modification protects the peptide from rapid enzymatic degradation, extending its active half-life relative to standard Selank. Provides anxiolytic, nootropic, and immunomodulatory effects comparable to or exceeding standard Selank with potentially greater duration from each dose.
Full profile| Leucine Enkephalin (Leu-Enkephalin) | N-Acetyl Selank | |
|---|---|---|
| Category | Nootropic & Cognitive | Nootropic & Cognitive |
| Also known as | Leu5-enkephalin, YGGFL, L-enkephalin, endogenous opioid pentapeptide | Selank-A, N-Ac-Selank, acetylated selank, N-acetyl selank |
| Evidence | Research-stage | Research-stage |
| Dosing range | 0.1mg–1mg mg, Intranasal or SC; extremely short half-life requires frequent dosing or continuous delivery | 100mcg–500mcg mcg, 1–2x daily intranasal |
| Administration | Intranasal, Subcutaneous injection, Intraventricular (research only) | Intranasal spray, 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 (acute), Fatigue, Headache (rare), Nasal irritation (intranasal route) |
| Cited sources | 2 references | 2 references |
Key differences
- Administration: Leucine Enkephalin (Leu-Enkephalin) — Intranasal, Subcutaneous injection, Intraventricular (research only); N-Acetyl Selank — Intranasal spray, Subcutaneous injection.
- Dosing units differ: Leucine Enkephalin (Leu-Enkephalin) is dosed in mg, N-Acetyl 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; N-Acetyl Selank is 1–2x daily intranasal.
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.
N-Acetyl Selank
N-Acetyl Selank shares Selank's core mechanism — BDNF/NGF upregulation, enkephalinase inhibition, and GABA-A receptor complex modulation — with improved metabolic stability from the N-terminal acetyl group. The acetyl modification protects against aminopeptidase N and angiotensin-converting enzyme cleavage, extending the peptide's active residence time in neural tissue after intranasal administration.
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.