Effects of pentazocine on the intestine and biliary tract of the rabbit in vitro.

Pentazocine impairs peristaltic activity and relaxes longitudinal muscle in the colon and in the ileum. The circular coat is excited in the colon, while in the ileum pentazocine exhibits both excitatory and inhibitory effects depending on the concentration employed. Pentazocine does not exert a spasmogenic effect in the smooth muscle of terminal bile duct but instead reduces the electrically-induced contraction. The effect of pentazocine does not seem to involve endogenous acetylcholine or catecholamine release.