Displacement by metiamide of the dose-response curves to pentagastrin and methacholine in the conscious rat.

1. The effect of a specific histamine H2-receptor antagonist, metiamide, on the acid dose-response curves for pentagastrin or methacholine was studied in rats provided with Heidenhain pouches. 2. Metiamide induced a shift to the right of the dose-response curve to pentagastrin and lowered the maximal secretion. 3. In contrast, metiamide only increased the ED50 for methacholine but did not alter the calculated maximal response. 4. The effect of metiamide on pentagastrin and methacholine-induced secretion is in agreement with the previously suggested difference in the part played by mucosal histamine in the mode of action of the two stimulatory agents.