The effects of substituted benzamides on frog rectus abdominis.

The substituted benzamides metoclopramide, bromopride, tiapride and sulpiride (10(-5) and 10(-4) M) significantly increased the sensitivity of frog rectus abdominis muscle to exogenous acetylcholine but not to carbachol. This supersensitivity could be correlated with the anticholinesterase activity of these drugs measured in homogenates from frog skeletal muscle. Sultopride, like procainamide, has only inhibitory effects on the responses of the rectus abdominis to acetylcholine and has no anticholinesterase activity in this preparation.