Histamine receptors in peripheral vascular beds in the cat.
1. The vasodilator activity of histamine has been studied in anaesthetized cats. 2. Histamine causes dose-dependent vasodilatation in the vasculature of the hind-limb and mesentery, perfused with blood at constant flow. 3. Experiments using the selective antagonists mepyramine and metiamide indicate the involvement of both H1- and H2-receptors in the vasodilator responses to histamine. Mepyramine (2.5 X 10(-6) mol/kg), causes displacement of the histamine dose-response curve. This displacement is maximum with a dose-ratio of about 10. Further dose-dependent displacement of the dose-response curve occurred after metiamide (4 X 10(-7) mol kg-1 min-1 and 2 X 10(-6) mol kg-1 min-1), although these doses of metiamide had no effect on histamine responses in the absence of mepyramine. 4. Vasodilator responses could also be elicited by the selective H1-receptor agonists, 2-methylhistamine, 2-(2-aminoethyl)pyridine and 2-(2-aminoethyl)thiazole and the selective H2-receptor agonist, 4-methylhistamine. 5. The selectivity of mepyramine and metiamide as histamine receptor antagonists was confirmed by their failure to reduce the vasodilator responses to acetylcholine, isoprenaline and bradykinin.
D000818:Animals; D001808:Blood Vessels / Q000187:drug effects*; D002415:Cats; D005260:Female; D005263:Femoral Artery / Q000187:drug effects; D006614:Hindlimb / Q000098:blood supply; D006632:Histamine / Q000031:analogs & derivatives / Q000502:physiology*; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects; D008785:Metiamide / Q000494:pharmacology; D011738:Pyrilamine / Q000494:pharmacology; D011955:Receptors, Drug / Q000187:drug effects*; D012039:Regional Blood Flow / Q000187:drug effects; D014666:Vasomotor System / Q000187:drug effects*
D011955:Receptors, Drug; D008785:Metiamide; D006632:Histamine; D011738:Pyrilamine