How Enkephalin Peptides Slow Down the Colon — The Delta Receptor Mechanism
Enkephalins inhibit relaxation nerve signals in human colon muscle through delta-opioid receptors, directly explaining one mechanism behind opioid-induced constipation.
Quick Facts
What This Study Found
Enkephalins inhibit non-adrenergic, non-cholinergic inhibitory neurotransmission in human colon through prejunctional delta-opioid receptors with high selectivity.
Key Numbers
How They Did This
Sucrose-gap technique measured electrical responses in human colon circular muscle. Multiple opioid agonists and antagonists were tested to determine receptor selectivity.
Why This Research Matters
This explains one mechanism by which opioids cause constipation. By blocking the nerve signals that normally relax the colon, opioid peptides reduce colon movement.
The Bigger Picture
This study identified the specific receptor mechanism behind opioid constipation in human tissue. By blocking the nerve signals that relax the colon, enkephalins effectively slow gut transit. This understanding has informed the development of peripherally-acting opioid antagonists (like methylnaltrexone) that treat opioid-induced constipation without affecting pain relief.
What This Study Doesn't Tell Us
In-vitro study using human tissue. The isolated tissue preparation removes normal neural network activity. Only one region of the colon was studied.
Questions This Raises
- ?Could delta-selective opioid antagonists specifically treat constipation without affecting pain relief?
- ?Are delta receptor levels altered in irritable bowel syndrome?
Trust & Context
- Key Stat:
- Delta receptors: 100x more potent than mu Delta-selective opioid agonists were 100-fold more effective than mu agonists at inhibiting colon relaxation nerve signals
- Evidence Grade:
- Moderate in-vitro study using human colon tissue with thorough pharmacological characterization. Directly relevant to human physiology.
- Study Age:
- Published in 1990. The delta-opioid mechanism of gut dysmotility has been validated and informs current approaches to managing opioid-induced constipation.
- Original Title:
- Enkephalins modulate inhibitory neuromuscular transmission in circular muscle of human colon via delta-opioid receptors.
- Published In:
- The Journal of physiology, 431, 465-78 (1990)
- Authors:
- Hoyle, C H, Kamm, M A, Burnstock, G, Lennard-Jones, J E
- Database ID:
- RPEP-00158
Evidence Hierarchy
Frequently Asked Questions
How does this relate to opioid-induced constipation?
The colon needs inhibitory nerve signals to relax and move contents along. Enkephalins block these signals through delta receptors, preventing normal relaxation cycles. This slows transit and causes constipation — the same mechanism behind opioid medication side effects.
Can this mechanism be blocked without affecting pain relief?
Yes. Drugs like methylnaltrexone block opioid receptors in the gut without crossing into the brain, relieving constipation while preserving pain relief. This study helped identify the specific receptor target.
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Cite This Study
https://rethinkpeptides.com/research/RPEP-00158APA
Hoyle, C H; Kamm, M A; Burnstock, G; Lennard-Jones, J E. (1990). Enkephalins modulate inhibitory neuromuscular transmission in circular muscle of human colon via delta-opioid receptors.. The Journal of physiology, 431, 465-78.
MLA
Hoyle, C H, et al. "Enkephalins modulate inhibitory neuromuscular transmission in circular muscle of human colon via delta-opioid receptors.." The Journal of physiology, 1990.
RethinkPeptides
RethinkPeptides Research Database. "Enkephalins modulate inhibitory neuromuscular transmission i..." RPEP-00158. Retrieved from https://rethinkpeptides.com/research/hoyle-1990-enkephalins-modulate-inhibitory-neuromuscular
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkPeptides research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.