Continuous recording of acid gastric secretion in the rat.

A method is described for the continuous recording of acid gastric secretion in the rat. The stomach of the rat anaesthetized with urethane is perfused with a dilute sodium hydroxide solution by way of the oesophagus and the pH of the fluid emerging from a cannula in the pylorus is registered graphically. In passing through the stomach, the perfusate collects sufficient buffer to act as an approximately linear buffer system over the relevant range, so that the change in pH becomes a measure of acid secretion. The preparation is suitable for the bioassay of secretory stimulants. Ten or more drug doses can be administered in succession in one preparation, so that each animal serves as a self-contained assay unit. Intravenous doses of histamine, methacholine, carbachol and acetylcholine produce a graded and reversible stimulation of acid secretion. The secretory effect of histamine is markedly and specifically potentiated by antihistaminases.