STUDIES WITH CHOLECYSTOKININ IN VITRO. III. MECHANISM OF THE EFFECT ON THE ISOLATED RABBIT GALL BLADDER STRIPS

¹ Department of Pharmacology, Mead Johnson Research Center, Evansville, Indiana

The effects of a number of autonomic drugs were studied for their interactions with cholecystokinin (CCK) on isolated rabbit gall bladder strips. In this preparation CCK produced contractions that were not prevented by cholinergic and alpha or beta adrenergic blockade and thus it seemed to act independently of the autonomic nervous system. Cyclic 3', 5'-adenosine monophosphate (cyclic AMP), theophylline, glucagon and isoproterenol relaxed the preparation whereas CCK, acetylcholine, serotonin, imidazole, methoxamine and oxymetazoline contracted the preparation. The effects of these agents on the intracellular levels of cyclic AMP were also directly determined. The hypothesis is advanced that CCK acted in this preparation either by mechanisms independent of cyclic AMP or by stimulating phosphodiesterase and lowering a small pool of cyclic AMP since the total cyclic AMP levels were not significantly reduced.