Effect of cholagogues on the volume of the gallbladder of dogs.

The effect of cholagogues on the volume of the gallbladder was studied by two-dimensional ultrasonography in six healthy dogs fasted for 24 hours. The volume was measured immediately before the administration of each test substance and at 10-minute intervals for 120 minutes thereafter. Tap water administered orally as a control did not elicit significant contractions; only the normal cyclic contractions of the gallbladder, occurring at intervals of 60 to 90 minutes, were recorded. Magnesium sulphate (500 mg as a 20 per cent aqueous solution given orally) and clanobutin (15 mg kg bodyweight-1 given intravenously) reduced the volume of the gallbladder by 24 per cent, and the volume then gradually increased at a rate which was almost identical for the two drugs. The cholagogic hormone cholecystokinin (administered intravenously at a dose rate of 0.04 microgram kg bodyweight-1) reduced the volume of the gallbladder by 40 per cent 10 minutes after its administration, and the volume was still markedly decreased 30 to 50 minutes after dosing. The results indicate that magnesium sulphate and clanobutin exert a direct effect on the motor activity of the gallbladder.