Identification of beta-adrenoceptors and histamine receptors in the cat nasal vasculature.

The responses of the nasal capacitance vessels of the cat were recorded following intra-arterial injections of beta-adrenoceptor agonists and histamine H1-and H2-receptor agonists. Isoprenaline evoked vasodilation and propranolol (beta-adrenoceptor antagonist) caused a parallel shift to the right of the isoprenaline log dose-response curve. Histamine, 2-(2-aminoethyl)pyridine (H1-agonist) and 4-methylhistamine (predominantly H2-agonist) all evoked vasodilation. Metiamide (H2-antagonist) produced a further small parallel shift to the right of the histamine log dose-response curve after the administration of mepyramine (H1-antagonist). It is concluded that the nasal capacitance vessels of the cat contain beta 2-adrenoceptors and H1-and H2-histamine receptors.