DEPLETION OF CATECHOLAMINES FROM RAT HEART BY PHENOXYBENZAMINE, TYRAMINE AND RESERPINE

Summary The effects of phenoxybenzamine and tyramine were examined on the catecholamine content of perfused rat heart The hearts were compared with those taken from reserpinized rats. Phenoxybenzamine and tyramine both caused a reduction in the intensity of the fluorescence which was characteristically that of noradrenaline, and the area of fluorescence associated with nerve bundles was reduced. These drugs also caused significant decreases in the concentrations of noradrenaline and adrenaline in the ventricle as determined by biological assay of extracts. In hearts from reserpinized rats, fluorescent material was absent and the noradrenaline and adrenaline contents were almost entirely depleted. These results suggest that the sympathomimetic action of phenoxybenzamine is due to release of catecholamines from stores in the heart.