Inhibition by cimetidine of the secretory and respiratory responses induced by theophylline and cyclic AMP in the amphibian gastric mucosa.

1. The effects of cimetidine, a histamine H2-receptor antagonist, on acid secretory and respiratory responses induced by histamine, theophylline and dibutyryl cyclic AMP were investigated in the in vitro toad gastric mucosa. 2. Histamine- and theophylline-stimulated acid secretion was competitively inhibited by cimetidine. A significant but lesser degree of inhibition was observed on oxygen uptake. 3. Cimetidine significantly inhibited acid secretion and oxygen uptake stimulated by dibutyryl cyclic AMP. 4. The results may suggest that cimetidine may have an additional action beyond the point of cyclic AMP in the oxyntic cells.