Dopamine Receptor Blocking Activity of Sulpiride in the Canine Exocrine Pancreas

Open Access
Publisher Website
Google Scholar
Abstract
The inhibitory effect of sulpiride on dopamine receptors was investigated in the exocrine pancreas of dogs anesthetized with pentobarbital and with the stomach ligated at the pylorus. All test substances were given i.v. Dopamine, acetylcholine, histamine and secretin produced a dose-related increase in pancreatic juice secretion, though the dose-effect curves of these secretagogs differed in shape. Epinephrine, norepinephrine, isoproterenol, methamphetamine and serotonin had no secretagog effects. The effects of acetylcholine and histamine were inhibited by atropine and cimetidine, respectively. The effect of dopamine was blocked by haloperidol, but not by atropine, cimetidine, phentolamine and propranolol. Dopamine may act on specific dopamine receptors related to the exocrine pancreatic secretion. Haloperidol had no effect on the effects of acetylcholine and histamine, but did inhibit the secretin-induced secretion, though the inhibitory effect was to a lesser extent than on the dopamine response. Sulpiride and chlorpromazine also suppressed dose-dependently the dopamine-induced secretion. The inhibitory activity of sulpiride was almost the same as that of haloperidol and 12 times more potent than that of chlorpromazine. Sulpiride was a potent dopamine antagonist in the canine exocrine pancreas.