Selective blockade of dopamine-induced vasodilation by ergonovine maleate in the vasculatures of dogs and rabbits.

In urethane anesthetized rabbits, ergonovine maleate significantly attenuated dopamine-induced systemic hypotension. Initial pressor responses to dopamine were significantly prolonged and potentiated by ergonovine. Mesenteric vasodilation elicited by dopamine in dogs was competitively inhibited by ergonovine at doses of 0.09 and 0.18 mg/kg, i.a. Failure of ergonovine to inhibit vasodilatory responses to acetylcholine or isoproterenol suggested selective blockade. These results confirm existing evidence that ergonovine selectively antagonizes peripheral dopaminergic receptors subserving vasodilation.