Chloroethylclonidine unmasks a non-alpha-adrenoceptor noradrenaline binding site in the rat aorta.
The effect of chloroethylclonidine on noradrenaline-induced contractions of the rat aorta was studied. Chloroethylclonidine (1-5 X 10(-5) M) shifted noradrenaline dose-response curve to the right approximately 5000-fold without depressing the maximum. The response to noradrenaline after chloroethylclonidine was not antagonized by phenoxybenzamine (10(-7) M), prazosin (10(-7) M), WB 4101 (10(-7) M) nor yohimbine (10(-5) M) and is therefore not mediated via alpha 1-adrenoceptors. These results would suggest that there is a homogenous population of chloroethylclonidine-sensitive alpha 1-adrenoceptors in the rat aorta and that chloroethylclonidine treatment reveals a non-alpha-adrenoceptor noradrenaline binding site in this tissue.
Oriowo
M A
MA
Department of Pharmacology, College of Medicine, University of Vermont, Burlington 05405.
Bevan
J A
JA
D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000378:metabolism; D003000:Clonidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004146:Dioxanes / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism*; D010643:Phenoxybenzamine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D011941:Receptors, Adrenergic / Q000187:drug effects*; D015016:Yohimbine / Q000494:pharmacology
D004146:Dioxanes; D011941:Receptors, Adrenergic; D010643:Phenoxybenzamine; D015016:Yohimbine; C051731:chlorethylclonidine; C010654:(2-(2',6'-dimethoxy)phenoxyethylamino)methylbenzo-1,4-dioxane; D003000:Clonidine; D009638:Norepinephrine; D011224:Prazosin