Possible Involvement of Endogenous Substances in the Cardiovascular Actions of Dopamine

Abstract

The dose-dependent positive chronotropic effects of dopamine were potentiated by dopamine antagonists in pithed dogs. The effects of dopamine were also potentiated but those of norepinephrine were not affected after treatment with indomethacin. When the drugs were directly administered to the sinus node artery, the dose-dependent positive chronotropic effects of dopamine were reduced during infusion with PGE1 but this inhibition was completely antagonized by pretreatment with droperidol, whereas those of isoproterenol were not affected by either PGE1 or droperidol. In isolated atrial preparations of guinea pig, the dose-dependent positive chronotropic effects of PGE1 were inhibited by droperidol and chlorpromazine but not by bulbocapnine, while those of isoproterenol were not affected by these dopamine antagonists. The increases of renal blood flow elicited by dopamine and bradykinin were similarly potentiated after treatment with indomethacin in dogs. The increases elicited by dopamine were reduced but those by isoproterenol were not affected after cinnarizine. The results suggest that PGE-type are involved in the negative chronotropic action of dopamine and that the dopamine antagonists antagonize the cardiac action of PGE1. It is therefore probable that PGE-type released by dopamine may exert in part the dopamine specific receptor action in the heart.