Kinetics of intra operative pH of the canine corpus fundal mucosa before and after truncal vagotomy.

The intra-operative surface pH of the corpus fundic mucosa in anaesthetized dogs was studied with a glass electrode during stimulation with graded doses of pentagastrin. The mucosal pH could be related to the dose of pentagastrin by a hyperbolic curve. With intact vagus ED50 averaged 0.67 micrograms kg-1 h-1 of pentagastrin and maximum effect corresponded to an average pH of 1.9. Immediately after truncal vagotomy there was a significant shift of the curve to the right corresponding to an average ED50 of 3.77 micrograms kg-1 h-1, an effect that could be described as that of a competitive inhibitor. Two weeks after vagotomy the value of ED50 had returned to the prevagotomy level. The high ED50 immediately after vagotomy is ascribed to the sudden fall in the subthreshold release of acetylcholine previously supplied by the intact vagus. The return to the low ED50 2 weeks later could be explained by denervation supersensitivity. The relation between the curves before and immediately after vagotomy suggests that the dose of the agonist be as low as possible, when testing the completeness of a vagotomy intra-operatively.