Inhibition of peristalsis in guinea-pig isolated ileum and colon by drugs that block prostaglandin synthesis.

1 Methods of analysing peristaltic activity have been evaluated by the use of recordings of longitudinal and circular muscle activity and of propulsion in whole segments of guinea-pig ileum and colon. 2 Some prostaglandin synthesis inhibitors, and antagonists of prostaglandin action were tested for their suitability for studying the role of prostaglandins in peristalsis. Aspirin was suitable; at 10-200 mug/ml it had little effect on responses of longitudinal muscle strips of the guinea-pig ileum to acetylcholine (ACh), histamine, nicotine or prostaglandin E2. Indomethacin (1-4 mug/ml) reduced responses to nicotine and prostaglandin E2. The prostaglandin antagonists polyphloretin phosphate and SC-19220 reduced contractions of ileal longitudinal muscle caused by nerve excitation with either nicotine or transmural stimulation. 3 Aspirin (20-100 mug/ml) or indomethacin (1-4 mug/ml) applied serosally greatly inhibited all aspects of peristalsis in guinea-pig ileum and colon. Inhibition of peristalsis of the ileum by aspirin was antagonized by prostaglandin E2 and that by indomethacin was removed by prostaglandin F2alpha or ACh. Inhibition of colonic peristalsis by aspirin was antagonized by prostaglandin E2 but rarely by ACh, and that by indomethacin by prostaglandin E1 or E2. Mucosal application of aspirin had little effect on either ileum or colon but indomethacin caused some inhibition. 4 These results support the supposition that prostaglandins contribute to peristaltic activity.