Influence of autonomic drugs on the motility of the sphincter of Oddi in the opossum

We have evaluated the effect of various autonomic drugs on the electromyographic activity of the sphincter of Oddi and the small intestine of seven opossums. Hexamethonium bromide and atropine sulfate abolished and bethanechol increased the frequency of spike bursts in the sphincter of Oddi and duodenum. Phenylephrine and epinephrine increased the number of spike bursts in the sphincter of Oddi after a short period of stimulation. No spike potentials were seen in the duodenum after infusion of norepinephrine. Clonidine and dobutamine decreased spike burst activity in the sphincter of Oddi and duodenum. Terbutaline also decreased the frequency of spike bursts in the sphincter of Oddi but did not change the number in the duodenum. Prior infusion of antagonists blocked partially or totally the effect of all respective agonists except for yohimbine, which did not inhibit the effect of clonidine. These findings suggest that the sphincter of Oddi may have cholinergic, alpha 1, alpha 1, beta 1 and beta 2-adrenergic receptors. Cholinergic agonists stimulate and alpha 2, beta 1 and beta 2-adrenergic agonists inhibit the motility of the sphincter of Oddi and the small intestine. Alpha-adrenergic agonists stimulate the motility of the sphincter of Oddi and inhibit the motility of the small intestine