Effect of atropine and truncal vagotomy on the exocrine pancreatic function in dogs stimulated with intraduodenal tryptophan.

The purpose of this experimental study was to analyze the effect of different doses of atropine and bilateral transthoracic truncal vagotomy on pancreatic secretion. We chose the dog as our experimental model and used the modified Thomas method to obtain gastric juice, removing the gastric acid with a gastric cannula. An additional duodenal cannula was used for the selective intubation of the greater pancreatic duct in order to obtain pure pancreatic juice. To stimulate pancreatic secretion the pancreas was stimulated with intravenous secretin at a constant dose and intraduodenal tryptophan at gradually increasing doses. The juice was collected at 10-min intervals and volume, output of bicarbonate and protein were determined. The results obtained show that low doses of atropine (0.65, 1.25 and 5 micrograms/kg/h) strengthen the suppressive effect of truncal vagotomy on the hydrobicarbonate secretion. Greatest suppression was found in the highest dosage of atropine in response to the intraduodenal tryptophane at gradually increasing doses. The above results suggest the possible existence of local enteropancreatic cholinergic reflexes that are readily suppressed by atropine and vagotomy. Suppression is not global though, since there is no significant reduction in the pancreatic protein secretion, which shows a dosage-effect curve in response to the gradually increasing doses of intraduodenal tryptophan released by the action of endogenous cholecystokinin. Our hypothesis is that there exists a nonvagal enteropancreatic cholinergic reflex.