Influence of cholinergic stimuli on gastric secretory responses to histamine in the dog

The effect of combined cholinergic and histamine stimulation on gastric secretion was investigated in 5 trained dogs in whom esophagostomy and gastrostomy had been performed and the MHR (acid secretory response to maximal histamine stimulation) had previously been established. Mecholyl and sham feeding were employed as cholinergic stimuli, and the effect of “periodic activity” of the digestive tract on the response to histamine stimulation was also studied. Potentiation with regard to acid secretion was evident when Mecholyl was superimposed on small or moderate doses of histamine, and to pepsin secretion when histamine was superimposed on Mecholyl. The mean maximum acid output in response to combined cholinergic and histamine stimulation (MAOHC) ranged from 5.6 to 12.9 mEq./15 min., and was significantly greater than the respective MHR values in 4 of 5 dogs. The MAOHC was found to be a linear function of the volume of the acid-bearing mucosa. A series of experiments with graded doses of Mecholyl suggested a quantitative relationship between Mecholyl dosage and acid output, pepsin output, and secretory volume, and confirmed the previously reported dosage-reversal effect of very large doses of Mecholyl on gastric secretion.