ANTAGONISM BY DROPERIDOL OF DOPAMINE-INDUCED RELAXATION IN ISOLATED DOG ARTERIES

Dopamine caused a dose-related relaxation in helically cut strips of dog coronary and renal arteries treated with phenoxybenzamine and contracted with prostaglandin F2α. The dose-response curve to dopamine was shifted to the right by droperidol in concentration above 3 × 10-5 M. Adenosine-induced relaxations were not attenuated by droperidol. The dose-relaxation curve to isoproterenol was also shifted to the right by droperidol. Propranolol (10-6 M) failed to significantly alter the dose-response curve to dopamine, and in propranolol-treated preparations the antognism by droperidol of dopamine actions was practically identical with that in control preparations. Droperidol appears to act as a reversible, surmountable antagonist to dopamine actions on dog arterial smooth muscles, and such evidence supports the hypothesis of specific dopamine receptors in dog arteries. © 1979.