Mechanical and metabolic effects of beta-receptor stimulators, the C-terminal octapeptide of cholecystokinin, and prostaglandin E2 on the isolated, depolarized sphincter of Oddi.

Similar to their actions on normally polarized, isolated sphincter of Oddi, the beta-receptor stimulators isoprenaline and tebutaline, and prostaglandin E2 produced relaxation of the depolarized preparation. The relaxation was accompained by an increase in the intracellular content of cyclic AMP. In contrast to its relaxing effect on normally polarized sphincter preparations, the C-terminal octapeptide of cholecystokinin (C8-CCK) contracted or had no effect on the depolarized sphincter. There was no change or a small decrease in the content of cyclic AMP in the muscle. It is suggested that the relaxing effects of beta-receptor stimulators and prostaglandin E2 on isolated sphinceter of Oddi, and the simultaneous increase in cyclic AMP-content are mediated processes independent of the electrical acitivty of the membrane. However, C8-CCK mediated relaxation and increase in cyclic AMP is dependent on the membrane potential.