Stimulation by McN-A-343 and blockade by telenzepine of acid secretion in the mouse isolated stomach at histamine-liberating cells.

(1) In the lumen-perfused mouse stomach in vitro, potential sites of gastric antisecretory action of the muscarine M1-receptor antagonist telenzepine were investigated. Acid secretion was stimulated by the muscarinic agonist McN-A-343 (1-1000 mumol/l). Neither basal nor McN-A-343-stimulated acid secretion was affected by 1 mumol/l TTX indicating that neuronal structures were probably not involved. (2) Acid secretion stimulated by 10 mumol/l McN-A-343 was inhibited by telenzepine (0.1-1.4 mumol/l) and cimetidine (10-140 mumol/l). Neither of the antagonists affected basal acid secretion. TTX had no inhibitory influence on the antagonist effect of telenzepine and cimetidine. (3) Compound 48/80 (100 mumol/l), which depletes histamine stores, initially mimicked but subsequently prevented the effect of McN-A-343. Prenylamine (50 mumol/l), which prevents histamine release, also abolished the secretagogue effect of subsequently administered McN-A-343. (4) Up to concentrations greater than 100 mumol/l, McN-A-343 did not stimulate acid production in rabbit isolated fundic glands and guinea-pig isolated parietal cells. Thus, parietal cells are not directly stimulated by McN-A-343. (5) Based on the site of action of the agonist McN-A-343 in the mouse isolated stomach and its failure to stimulate parietal cells from different species directly, it is concluded that telenzepine blocks, in the mouse isolated stomach, muscarine receptors located on paracrine cells to reduce endogenous histamine release.