The effects of intravenous 6-hydroxydopamine on peripheral alpha-adrenoreceptors.
1 Peripheral alpha-adrenoreceptor-mediated responses were studied in conscious intact rabbits and in animals pretreated with intravenous 6-hydroxydopamine (50 mg/kg). 2 Treatment caused a large decrease in noradrenaline in plasma and peripheral tissue but only small falls in blood pressure. 3. There was a shift to the left in pressor dose-response curves to the alpha 1-adrenoreceptor agonist phenylephrine and the mixed alpha 1/alpha 2-adrenoreceptor agonist noradrenaline in 6-hydroxydopamine-pretreated animals. The alpha 1-adrenoreceptor antagonist prazosin was less effective at blocking the phenylephrine pressor response in these animals. 4 There was no change in pressor responses to the alpha 2-adrenoreceptor selective agonists clonidine and guanabenz and alpha-adrenoreceptor antagonists were equally effective at blocking this pressor response in 6-hydroxydopamine-pretreated and in intact rabbits. 5 In conscious animals 6-hydroxydopamine pretreatment causes alteration in responses mediated by postsynaptic alpha 1-but not postsynaptic alpha 2-adrenoreceptors. These changes may help maintain blood pressure in the 6-hydroxydopamine treated rabbits.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D003000:Clonidine / Q000494:pharmacology; D006143:Guanabenz / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects; D006892:Hydroxydopamines / Q000494:pharmacology*; D008297:Male; D009638:Norepinephrine / Q000097:blood; D010646:Phentolamine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011817:Rabbits; D011941:Receptors, Adrenergic / Q000187:drug effects*; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D014018:Tissue Distribution
D006892:Hydroxydopamines; D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D010656:Phenylephrine; D006143:Guanabenz; D003000:Clonidine; D009638:Norepinephrine; D010646:Phentolamine