Pharmacological analysis of the effects of substituted benzamides on the isolated guinea-pig ileum. Study of metoclopramide, sulpiride, bromopride, tiapride and sultopride.

The effects of metoclopramide (Mcp), sulpiride (Sp) and some of their derivatives: bromopride (Br), tiapride (Ti) and sultopride (Stp) have been compared on the guinea-pig isolated ileum. 1. Br and Ti have, like Mcp, and indirect cholinergic stimulating effect on the intestinal smooth muscle. Sp and Stp are devoid of such an effect. 2. At high doses, all the benzamides have a direct inhibitory effect on the ileum. 3. Mcp, Br and Ti (10(-5)M) potentiate the responses of the ileum to acetylcholine (ACh). At high doses (10(-4)M) the effects of all benzamides on the responses to ACh as well as to histamine (H) are mostly inhibitory. 4. Mcp and Br (10(-5)M) inhibit the responses of the ileum to serotonin (5HT) while Ti, Sp and Stp potentiate them. 5. Neural pathways and calcium mechanisms are involved in the potentiations of ACh and 5HT responses since the enhancements observed are abolished in the presence of tetrodotoxin or in the absence of Ca++.