Effect of Histamine Upon the Salivary Flow Induced by Pilocarpine in Dogs.

Abstract

In the course of an investigation of the variations in the flow and composition of saliva secreted in response to different types of stimuli, histamine was tried among other pharmacological agents, chiefly because of reports in the literature on its effects upon the salivary glands. These reports refer to acute experiments upon anesthetized or decerebrated animals. Our experiments were made on unanesthetized dogs with permanent fistulae of one of the submaxillary glands, and, aside from obvious advantage of using such animals, it made it possible to repeat an experiment on the same dog several times under identical or different conditions. The 3 dogs used had been accustomed to being placed in a stand and having a measuring tube attached to the lower jaw.

Subcutaneous injections of 1 to 5 gm. of histamine sulphate were not followed by any secretion of saliva. To bring out the possible effect of histamine upon the salivary flow elicited by other means, the dogs were given subcutaneous injections of 1 mg. histamine sulphate, followed 20 minutes later by a subcutaneous injection of 1/3 mg. pilocarpine sulphate per kg. The quantity of saliva secreted under these conditions was compared with that elicited by a similar dose of pilocarpine, not preceded by histamine. This was repeated several times on each dog, histamine-pilocarpine alternating with pilocarpine only experiments. The results in all 3 dogs indicate that a previous injection of histamine inhibits the flow of saliva which follows the administration of pilocarpine. Thus in one dog pilocarpine alone caused a flow of saliva from the fistula amounting on different occasions to 54.9, 48.9, 39.7, and 46.9 cc. per hour (average, 47.6 cc), whereas in experiments with pilocarpine after histamine, the corresponding amounts of saliva were 31.9, 26.6, 37.6, and 33.8 cc. (average, 32.5 cc).