UPTAKE OF 3H-NOREPINEPHRINE BY FLUORESCENT NERVES OF THE HEART

The localization of uptake 5 minutes after the injection of a low dose of 3 H-norepinephrine by adrenergic nerve fibers in the heart has been observed by combining autoradiography with the formaldehyde-induced histochemical fluorescence method for aromatic monoamines in the same tissue section. The distribution of 3 H-label corresponds exactly to that of the fluorescent nerves. Furthermore, uptake studies in animals depleted of catecholamines by the tyrosine hydroxylase inhibitor (H 44/68), which does not block uptake, indicate that the dosage of 3 H-norepinephrine used, under the conditions of the present experiment, was not in itself sufficient to produce the intense formaldehyde-induced fluorescence in nerves. It may be concluded that 3 H-norepinephrine was taken up only by those nervous structures in the heart which show a specific fluorescence reaction due to the presence of endogenous catecholamine.