THE EFFECTS OF INTRAVENOUS 6‐HYDROXYDOPAMINE ON PERIPHERAL α‐ADRENORECEPTORS

Publisher Website
Google Scholar
Abstract
Peripheral α‐adrenoreceptor‐mediated responses were studied in conscious intact rabbits and in animals pretreated with intravenous 6‐hydroxydopamine (50 mg/kg). Treatment caused a large decrease in noradrenaline in plasma and peripheral tissue but only small falls in blood pressure. There was a shift to the left in pressor dose‐response curves to the α‐adrenoreceptor agonist phenylephrine and the mixed α1/α2‐adrenoreceptor agonist noradrenaline in 6‐hydroxydopamine‐pretreated animals. The α1‐adrenoreceptor antagonist prazosin was less effective at blocking the phenylephrine pressor response in these animals. There was no change in pressor responses to the α2‐adrenoreceptor selective agonists clonidine and guanabenz and α‐adrenoreceptor antagonists were equally effective at blocking this pressor response in 6‐hydroxydopamine‐pretreated and in intact rabbits. In conscious animals 6‐hydroxydopamine pretreatment causes alteration in responses mediated by postsynaptic α1‐but not postsynaptic α2‐adrenoreceptors. These changes may help maintain blood pressure in the 6‐hydroxydopamine treated rabbits.