Abstract: Carbenoxolone, the succinyl ester of glycyrrhetinic acid, is now used in clinical treatment of ulcer diseases. The effects of carbenoxolone, a gap junction channel blocker, on the contractile responses of the isolated rat colon and the isolated guinea-pig ileum were studied. Carbenoxolone reduced amplitude of the spontaneous mechanical activity of the isolated rat colon and guinea-pig ileum. A similar inhibitory effect of carbenoxolone was observed on contractile responses of the isolated rat colon and guinea-pig ileum to electrical field stimulation and acetylcholine. Carbenoxolone could have inhibitory effects on neuromuscular transmission in the isolated rat colon and guinea-pig ileum and seems this effects unrelated to uncoupling effects of it.