Effect of Atropine on Histamine-Stimulated Gastric Secretion in the Dog

¹ From the Gastroenterology Research Laboratory, Mount Sinai Hospital, New York City

Inhibitory effect of atropine on gastric acid secretion was studied in four dogs with vagally denervated corpus pouches, stimulated by 0.025 mg of histamine-base subcutaneous every 10 minutes. The mean inhibition of acid output in the 3rd hour after subcutaneous injection of atropine sulphate was 29% at 0.1 mg/kg body weight, 31% at 0.2 mg/kg, and 96% at 0.4 mg/kg. At the highest dosage, inhibition was virtually complete in six of seven experiments. Since current concepts of cholinergic blocking action by atropine on gastric secretion are not completely explanatory of the present results, possible alternative formulations of the role of acetylcholine and histamine in stimulating the parietal cell are presented. One of these postulates that histamine is the final common chemical pathway for all stimuli to the acid secreting cell. The existing evidence for this is reviewed briefly. In addition, further striking evidence is presented to support the hypothesis that the primary (parietal cell) acidity is relatively constant and independent of the secretory rate.