Bradykinin reverses the effect of opiates in the gut by enhancing acetylcholine release

Four naturally occurring peptides of the kinin family, bradykinin, lysylbradykinin, methionyllysylbradykinin, and polisteskinin reverse the inhibitory effect of morphine, metenkephalin, and epinephrine on the electrically stimulated guinea pig ileum longitudinal muscle myenteric plexus preparation. Bradykinin, the most potent kinin, enhances the release of acetylcholine in the gut, and its reversal of the opiate inhibitory effect is blocked by the anticholinergic drug, hyoscine.