ALPHA-ADRENOLYTIC PROPERTIES OF BROMOCRIPTINE IN DOGS

  • 1 January 1982
    • journal article
    • research article
    • Vol. 260  (1) , 83-90
Abstract
The effects of bromocriptine on dose-response curves to i.v. administered sympathomimetic agents (adrenaline [epinephrine], noradrenaline [norepinephrine], phenylephrine and clonidine) were studied in normotensive anesthetized dogs. After pretreatment with bromocriptine (0.3 or 1 mg/kg i.v.) low doses of adrenaline showed a significant depressor action. This drug failed to modify the variations in blood pressure induced by noradrenaline. Bromocriptine reduced the pressor effect of phenylephrine and the hypotensive action of clonidine. Apparently, in addition to dopaminergic stimulant properties, bromocriptine also possesses .alpha.-adrenolytic properties. The data obtained with phenylephrine and clonidine suggest that bromocriptine is a mixed .alpha.- and .alpha.2-antagonist. The differences observed between adrenaline and noradrenaline are disucssed in terms of different subtypes (intra- and extra-synaptic) of .alpha.-adrenoceptors.