Histamine H1- and H2-receptors in the gastric vasculature of the rabbit.

The histamine receptors in the rabbit blood perfused gastric vasculature were analysed pharmacologically. Histamine elicited a monophasic increase in perfusion pressure which was antagonized by mepyramine and enhanced by metiamide. The maximum observed response was enhanced by metiamide to that produced by a specific H1-receptor agonist. It is concluded that the gastric vasculature responds to histamine with an H1-receptor mediated vasoconstriction and an H2-receptor mediated dilatation. In this preparation the H1-effect predominates in response to injection of histamine.