Effects of pimozide on the response of smooth muscle to non-dopamine agonists and calcium.

Pimozide inhibits acetylcholine and histamine-induced contractions of the isolated guinea-pig ileum and noradrenaline-induced contractions of the isolated rat vas deferens in a non-competitive manner. In order to explore the nature of this inhibitory effect, we investigated pimozide's effects on calcium-induced contractions of deplorized guinea-pig ileum. In this case the antagonism elicited was competitive. Therefore caution is indicated in the use of pimozide to provide indirect proof of the existence of peripheral dopamine receptors.