About Leu-Enkephalin
Binds delta and mu opioid receptors in the CNS and periphery. Modulates pain signal transmission in dorsal horn neurons. Also activates opioid receptors on immune cells, influencing cytokine production and immune cell trafficking.
Leucine enkephalin (Leu-enkephalin; Tyr-Gly-Gly-Phe-Leu) is an endogenous opioid pentapeptide derived from proenkephalin A, co-discovered by John Hughes and Hans Kosterlitz in 1975 alongside methionine enkephalin as the first endogenous ligands identified for opiate receptors in the mammalian brain. Leu-enkephalin binds preferentially to delta opioid receptors and to a lesser extent mu receptors, producing analgesic effects and modulating pain signal transmission at spinal and supraspinal levels including the periaqueductal gray; rodent pharmacology studies have established its antinociceptive role in descending pain modulation pathways alongside other endogenous opioids. Exogenous administration of leu-enkephalin faces fundamental pharmacological barriers including a very short plasma half-life (seconds to minutes), near-complete first-pass metabolism by peptidases, and poor blood-brain barrier penetration, which have prevented its clinical development as an analgesic and explain the absence of human therapeutic trials. Leu-enkephalin is an endogenous opioid peptide with no FDA approval or therapeutic indication in any jurisdiction; it is a research tool compound used in receptor pharmacology and pain biology studies, and any provider listing should be understood as an educational reference rather than as a claim of established therapeutic utility.
Leu-Enkephalin Benefits & Research Areas
Regulatory & Evidence
Research Evidence
Risk Profile
Moderate risk profile in research contexts. Review contraindications and administration guidelines before use.
Regulatory Status
- Availability Status
- Research Only
- FDA Status
- Not Evaluated
Regulatory status reflects publicly available information and may change. This is not legal or medical advice.
Research Sources
1 source cited · 1 moderate
1 Animal
Comparison of the antinociceptive action of mu and delta opioid receptor ligands in the periaqueductal gray matter, medial and paramedial ventral medulla in the rat
Brain Research · 1986
Research in rats using intracerebral microinjection found that delta opioid receptor agonists including leu-enkephalin analogs (DADL) produced dose-dependent antinociceptive effects in the periaqueductal gray and produced maximum blockade of spinally mediated pain responses in the medullary reticular formation via mechanisms distinct from mu opioid receptor ligands.
Leu-Enkephalin Side Effects & Safety Considerations
Moderate risk profile. Review all reported considerations carefully before use.
Reported contraindications & considerations
Consult a qualified healthcare professional before making any health decisions. This information is educational only and does not constitute medical advice.
Where to Buy Leu-Enkephalin — Providers & Availability
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Questions to Ask Your Provider
Frequently Asked Questions — Leu-Enkephalin
Leucine enkephalin (Leu-enkephalin; Tyr-Gly-Gly-Phe-Leu) is an endogenous opioid pentapeptide derived from proenkephalin A, co-discovered by John Hughes and Hans Kosterlitz in 1975 alongside methionine enkephalin as the first endogenous ligands identified for opiate receptors in the mammalian brain. Leu-enkephalin binds preferentially to delta opioid receptors and to a lesser extent mu receptors, producing analgesic effects and modulating pain signal transmission at spinal and supraspinal levels including the periaqueductal gray; rodent pharmacology studies have established its antinociceptive role in descending pain modulation pathways alongside other endogenous opioids.
pain modulation, anti-inflammatory, immune modulation.
Research on Leu-Enkephalin primarily documents effects related to pain modulation and anti-inflammatory and immune modulation. These are areas covered in preclinical and clinical literature — individual response varies and effects depend on context of use.
Reported contraindications and considerations for Leu-Enkephalin include cardiovascular condition, pregnant or nursing. This is educational information only — consult a qualified healthcare professional before use.
Research in rats using intracerebral microinjection found that delta opioid receptor agonists including leu-enkephalin analogs (DADL) produced dose-dependent antinociceptive effects in the periaqueductal gray and produced maximum blockade of spinally mediated pain responses in the medullary reticular formation via mechanisms distinct from mu opioid receptor ligands.