The effect of anaesthesia on the inhibition of pentagastrin-evoked gastric acid secretion induced by atropine in the rat.

1. In the anaesthetized, vagally intact rat, with a perfused gastric lumen, atropine produced a maximum inhibition of 60% of maximal pentagastrin-evoked gastric acid secretion. Sub-maximal pentagastrin-stimulated secretion was also inhibited by atropine.2. In the anaesthetized, vagotomized rat, with a perfused gastric lumen, atropine had no inhibitory effect on maximal pentagastrin-evoked gastric acid secretion.3. In the conscious fistula rat, atropine totally abolished both the basal gastric acid secretion and the maximal gastric acid secretion evoked by pentagastrin. In the anaesthetized chronic fistula rat, doses of atropine up to 1.6 mg.kg(-1) administered subcutaneously produced a maximum inhibition of 70% of maximal pentagastrin-evoked gastric acid secretion. Vagotomy did not affect the response to atropine.4. In the conscious Heidenhain pouch rat, doses of atropine up to 1.6 mg.kg(-1) administered subcutaneously produced a maximum inhibition of 70.9% of maximal pentagastrin-evoked gastric acid secretion. Both anaesthesia and vagotomy, alone or in combination, did not affect the response to atropine.