Cholecystokinin and cholinergic agents on periodic gallbladder contraction in dogs.

1. The effect of cholecystokinin octapeptide (CCK-OP), methacholine, 2-deoxy-D-glucose (2DG) and gastric distension on gallbladder contraction in relation to interdigestive activity was studied in four conscious dogs with chronic biliary fistulae. 2. The gallbladder contraction in response to CCK-OP was inhibited by atropine and by a ganglionic blocking agent, the characteristics suggesting competitive inhibition. 3. Spontaneous contraction of the gallbladder was still observed after the administration of CCK-OP, methacholine or 2DG. With ganglionic blockade, CCK(-)-OP or methacholine initiated gallbladder contraction, but the spontaneous peak was no longer observed. 4. CCK-OP (100 ng kg-1), methacholine or 2DG advanced the spontaneous contraction of the gallbladder, but did not alter the duration of the cycle. 5. Gastric distension initiated gallbladder contraction. This was abolished by ganglionic blockade. The contraction did not continue in spite of continuous gastric distension, and the spontaneous contraction reappeared 100 min following the pre-distension control.