On the Mechanism of Action for the Effect of Cholecystokinin on the Choledochoduodenal Junction in the Cat

The resistance of the choledochoduodenal junction was studied by measuring the flow from the common duct into the duodenum under constant infusion pressure and by measuring the intracholedochal pressure under constant infusion rate. It is concluded that the choledochoduodenal junction contains a real sphincter where the normal contracted state depends on an intact cholinergic nerve supply. As the effect of cholecystokinin on the small intestine is mediated by a cholinergic pathway, a similar mechanism of action for its effect on the choledochoduodenal junction was questioned. However, cholinergic and adrenergic mechanisms could be blocked by atropine and reserpine without affecting the antagonism of cholecystokinin to the contraction of the spincter elicited by bradykinin. Thus the effect of cholecystokinin on the choledochoduodenal junction seems to be a direct one and related rather to its effect on the gall‐bladder than to its effect on the small intestine.