A study of the effect of dopamine on adrenergic receptors.

Dopamine has been found to be present at various sites in the body (1). It acts as a precursor in the biosynthesis of norepinephrine and has also been ascribed a role of being a neurotransmitter (2). The effect of dopamine on the alpha adrenergic receptors is well established (3), but there are controversial reports regarding its beta receptor activity. Katz et al. (4) found that cyclopropane-dopamine and halothane-dopamine cardiac ar rhythmia is blocked by H 56/28, a beta adrenergic blocking agent. However, the specifi city of beta adrenergic blockers (especially pronethalol) has been questioned since some of them have local anaesthetic and quinidine like effects, which may account for their anti arrhythmic action (5-9). Eble (3) reported, that dopamine produces a depressor response after pre-treatment with alpha blocking agent, which is not blocked by a beta adrenergic blocking agent. McNay and Goldberg (10) pointed out that some of the effects of dopa mine might be exerted via "dopamine receptors" which are different from beta receptors. It was thus of interest to study the beta adrenergic activity of dopamine by using pro