INHIBITION OF SYMPATHOMIMETIC EFFECTS ON THE HEART

Abstract
The adrenaline β-receptor blocking drug, pronethalol, and the sympathomimetic amines, (–)-ephedrine, (–)-amphetamine, dexamphetamine, (–)-Ω-ephedrine and tyramine, inhibited the sympathomimetic effects of butyrylcholine and tyramine on the guinea-pig isolated atrium. Being reversible and noncompetitive, this antagonism was unspecific and not due to blockade of adrenaline receptors, although pronethalol inhibited the effect of noradrenaline competitively.