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The release of Met-enkephalin from the guinea-pig ileum at rest and during peristaltic activity
Abstract:
Segments of guinea-pig ileum maintained at an intraluminal pressure of 0cm H2O released methionine-enkephalin-like material (ME) into the bathing fluid. Elevation of intraluminal pressure to 5 cm H2O induced peristalsis and reduced ME release both in the absence and presence of naloxone (0.27 microM). Following prolonged distension, tissues developed intermittent peristaltic activity. ME release during intermittency was consistently and significantly (p less than 0.05) greater than that observed from tissues exhibiting continuous peristalsis. These results suggest that ME release is associated with nonpropulsive activity in the guinea-pig ileum.
Insights
Methionine-enkephalin-like material (ME) release in guinea-pig ileum decreases with induced peristalsis. However, ME release increases during intermittent peristaltic activity, suggesting a link to nonpropulsive actions.
Area of Science:
- Gastroenterology
- Neuroscience
- Pharmacology
Background:
- The guinea-pig ileum is a widely used model for studying gastrointestinal motility and neurochemical signaling.
- Methionine-enkephalin (ME) is an endogenous opioid peptide implicated in regulating gut function.
- Intraluminal pressure and mechanical distension are key factors influencing intestinal activity and peptide release.
Purpose of the Study:
- To investigate the relationship between intraluminal pressure, peristalsis, and methionine-enkephalin-like material (ME) release in the guinea-pig ileum.
- To determine if ME release is modulated by propulsive versus nonpropulsive intestinal activity.
- To explore the role of opioid receptors in ME release during ileal distension.
Main Methods:
- Segments of guinea-pig ileum were maintained under controlled intraluminal pressures (0 cm H2O and 5 cm H2O).
- Peristaltic activity and ME release into the bathing fluid were measured.
- The effects of naloxone, an opioid receptor antagonist, on ME release were assessed.
- ME release was compared between tissues exhibiting continuous peristalsis and intermittent peristaltic activity.
Main Results:
- At baseline intraluminal pressure (0 cm H2O), ME was released into the bathing fluid.
- Increasing intraluminal pressure to 5 cm H2O induced peristalsis and significantly reduced ME release.
- This reduction in ME release occurred irrespective of the presence of naloxone.
- Following prolonged distension, intermittent peristaltic activity emerged, during which ME release was significantly greater than during continuous peristalsis.
Conclusions:
- Methionine-enkephalin-like material release in the guinea-pig ileum is inversely correlated with propulsive peristaltic activity.
- ME release appears to be associated with nonpropulsive intestinal activity or the transition between propulsive and nonpropulsive states.
- These findings suggest a complex regulatory role for ME in modulating gut motility and potentially pain signaling within the enteric nervous system.