Effects of some drugs and peptide hormones on the responsiveness of the rabbit isolated gall-bladder to cholecystokinin.

1. The efficacies of some standard preparations of CCK were compared and the effects of some drugs and peptide hormones on the responsiveness of the rabbit isolated gall-bladder to cholecystokinin were studied with an established automatic method of estimating cholecystokinin. 2. Atropine, propranolol, phentolamine mesylate and lignocaine were shown to have no effect on the responsiveness of the rabbit isolated gall-bladder. 3. Glucagon, somatostatin, pentagastrin, pancreatic polypeptide, motilin and the Karolinska preparation of secretin had no effect on the preparation alone and caused only slight changes when given with cholecystokinin. 4. The Boots preparation of secretin exhibited a small cholecystokinin effect when given alone, but considerably inhibited cholecystokinin-induced contractions. 5. The desulphated C-terminal octapeptide of cholecystokinin also exhibited inhibitory effects.