Changed cholinergic receptor characteristics after vagotomy in gastric fistula dogs

By the use of small doses of atropine (0.2-10 mug/kg-h) the kinetics of atropine antagonism to the gastric stimuli Urecholine and pentagastrin could be defined in intact dogs and in dogs after fundic vagotomy. Though pentagastrin was a much less effective stimulus after vagotomy, atropine had very similar effects on the pentagastrin response before and after vagotomy. Stimulation of both acid and pepsin by Urecholine remained unchanged by vagotomy but was uncompetitively inhibited by atropine in the intact dog, suggesting irreversible binding of atropine to gastric cholinergic receptors. After vagotomy, however, atropine inhibited Urecholine competitively, suggesting that atropine was now bound reversibly to cholinergic receptors. These changes are analogous to those occurring in muscle after denervation and suggest the growth of new cholinergic receptors with changed characteristics after denervation of the stomach.