Effects of Metiamide and Propranolol on Gastric Secretion in Anesthetized Dogs

The effects of metiamide, a histamine H2-receptor antagonist, and propranolol, a beta-adrenergic blocking agent, on gastric secretion were studied in anesthetized dogs. Metiamide, 1.45 mg/kg i.v., markedly inhibited the gastric secretion induced by a continuous i.v. infusion of tetragastrin (8 microng/kg-hr), histamine dihydrochloride (160 microng/kg-hr), or methacholine bromide (100 microng/kg-hr). Propranolol 0.5 or 1.0 mg/kg i.v. produced a significant potentiation of tetragastrin-induced gastric secretion but no influence of the secretion induced by methacholine. Propranolol at 5 or 10 mg/kg i.v. produced a slight reduction of the tetragastrin-induced secretion and a significant reduction of methacholine-induced secretion. Histamine-induced gastric secretion was not affected by propranolol at either 1 and 10 mg/kg i.v. These findings lend support to the hypothesis that interactions among histamine, gastrin and acetylcholine receptors do occur though the degree would not be the same in all directions.