The effects of metoclopramide on acetylcholine release and on smooth muscle response in the isolated guinea-pig ileum

The effects of metoclopramide on smooth muscle contraction and on release of acetylcholine were studied in the guinea-pig myenteric plexus longitudinal muscle preparation. Acetylcholine was determined either as endogenous acetylcholine, or as labelled transmitter from strips preloaded with 3H-choline. Metoclopramide caused an increase in resting tension of longitudinal muscle as well as an increase in resting output of either endogenous or labelled acetylcholine. Tetrodotoxin abolished the metoclopramide-evoked increase in transmitter release. The increase in smooth muscle tension was clearly related to the increase in resting output. The effects of metoclopramide on both longitudinal muscl…