Possible involvement of histamine H2-receptors in the vasodilator effect of clonidine on isolated and perfused canine coronary arteries.
The mechanism of clonidine-induced vasodilatation was investigated in the isolated and perfused canine coronary arteries. Clonidine produced a slight vasoconstriction at small doses whereas it induced a dose-related vasodilatation at large doses (more than 3 micrograms). The vasodilatation was reversed to vasoconstriction by treatment with 100 micrograms of cimetidine (a selective H2-receptor antagonist) but was not affected by 100 micrograms of chlorpheniramine (a selective H1-receptor antagonist). These results suggest that clonidine can dilate the isolated and perfused canine coronary arteries by acting on histamine H2-receptors.
D000818:Animals; D002744:Chlorpheniramine / Q000494:pharmacology; D002927:Cimetidine / Q000494:pharmacology; D003000:Clonidine / Q000494:pharmacology*; D003331:Coronary Vessels / Q000187:drug effects; D004285:Dogs; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D010477:Perfusion; D011970:Receptors, Histamine H2 / Q000502:physiology*; D014664:Vasodilation / Q000187:drug effects*
D011970:Receptors, Histamine H2; D002744:Chlorpheniramine; D002927:Cimetidine; D003000:Clonidine