Peristalsis abolishes the release of methionine-enkephalin from guinea-pig ileum in vitro.

The release of methionine-enkephalin from superfused guinea-pig ileum has been demonstrated. Methionine-enkephalin, as measured by radioimmunoassay, was shown to be released from tissues maintained at an intraluminal pressure of O cm water (resting conditions). Increased intraluminal pressure (5 cm water) induced peristalsis and abolished the release of methionine-enkephalin. These results provide further evidence that endogenous opioids may be involved in the modulation of contractile activity in the guinea-pig ileum.