Histamine-induced vasodilations mediated by H1- and H2-receptors in isolated rat common carotid arteries.
Using the cannula inserting method, the vasodilatory effects of histamine were analysed employing selective histamine H1- and H2-receptor agonists and antagonists in isolated, perfused rat common carotid arterial preparations which were preconstricted by a continuous infusion of phenylephrine with propranolol. Histamine, 2-pyridylethylamine (2-PEA) (a selective H1-agonist) and dimaprit (a selective H2-agonist) produced a vasodilation in a dose-related manner. The order of potency was histamine greater than dimaprit greater than 2-PEA. Histamine-induced dilations were significantly inhibited by either diphenhydramine (a selective H1-antagonist) or cimetidine (a selective H2-antagonist). 2-PEA-induced dilations were significantly inhibited by diphenhydramine but not by cimetidine. Dimaprit-induced dilations were significantly blocked by cimetidine but not by diphenhydramine. ACh-, histamine-, 2-PEA- and dimaprit-induced dilations were significantly suppressed by removal of the endothelium. From these results, it is concluded that (1) isolated rat common carotid arteries have both H1- and H2-receptors, (2) there are few vasoconstrictory H1-receptors, (3) both H1- and H2-receptors mediate only vasodilation but not vasoconstriction, and (4) EDRF from the endothelium might participate in histamine-induced vasodilation via not only H1- but also H2-receptors.
Chiba
S
S
Department of Pharmacology, Shinshu University School of Medicine, Matsumoto, Japan.
Tsukada
M
M
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002339:Carotid Arteries / Q000187:drug effects*; D002927:Cimetidine / Q000494:pharmacology; D017259:Dimaprit; D004155:Diphenhydramine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D006632:Histamine / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011969:Receptors, Histamine H1 / Q000187:drug effects / Q000502:physiology*; D011970:Receptors, Histamine H2 / Q000187:drug effects / Q000502:physiology*; D012503:Saponins / Q000494:pharmacology; D013890:Thiourea / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects*
D011725:Pyridines; D011969:Receptors, Histamine H1; D011970:Receptors, Histamine H2; D012503:Saponins; D002927:Cimetidine; D006632:Histamine; D004155:Diphenhydramine; C006183:2-(2-aminoethyl)pyridine; D013890:Thiourea; D000109:Acetylcholine; D017259:Dimaprit