The mechanism of the vasodilator effects of histamine and 4-methylhistamine in the hindquarters of the cat.
Intraarterial administration of histamine and 4-methylhistamine induced a fall in perfusion pressure of perfused hindquarters of the chloralose-anesthetized cat. Mepyramine which is a histamine H1-receptor blocker competitively inhibited the depressor effect of histamine without altering that of 4-methylhistamine. Continuous intravenous infusion of metiamide, which is a histamine H2-receptor blocker, to the mepyramine treated cats caused a further inhibition in response to histamine as well as 4-methylhistamine. These results indicate that both histamine H1- and H2-receptors are present in the vasculature of the cat hindquarters and both of them are responsible for the vasodilator effect of histamine.
D000818:Animals; D002415:Cats; D005260:Female; D006632:Histamine / Q000494:pharmacology*; D008297:Male; D008761:Methylhistamines / Q000494:pharmacology*; D008785:Metiamide / Q000494:pharmacology; D011738:Pyrilamine / Q000494:pharmacology; D011969:Receptors, Histamine H1 / Q000187:drug effects; D011970:Receptors, Histamine H2 / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology*; D014666:Vasomotor System / Q000187:drug effects
D008761:Methylhistamines; D011969:Receptors, Histamine H1; D011970:Receptors, Histamine H2; D014665:Vasodilator Agents; D008785:Metiamide; D006632:Histamine; D011738:Pyrilamine