Effect of histamine on cyclic AMP levels in the submandibular gland.

Histamine and 4-methylhistamine increased on cyclic AMP level in chopped guinea-pig submandibular glands. 4-Methylhistamine was more active than histamine. 2-(2-Pyridyl)ethylamine was less active than histamine or almost inactive. Metiamide markedly antagonized the histamine-induced cyclic AMP increase but mepyramine had no inhibitory effect on this increase. These results suggest that there are H2-receptors which mediate the cyclic AMP response to histamine in the guinea-pig submandibular gland.