Abstract

The subcellular distribution of intraventricularly administered H3-norepinephrine and of endogenous catecholamine has been examined in the rat brain. Although the subcellular localization of exogenous and endogenous catecholamine is similar, the exogenous amine is more highly concentrated in the synaptosomal fraction. The specific activity of norepinephrine declines more rapidly in the supernatant than in the particulate fraction. The ratio of particulate to supernatant of H³-norepinephrine in the cerebellum is significantly lower than in the hypothalanmus, midbrain and neostriatum. Reserpine releases radioactive and endogenous norepinephrine preferentially from the supernatant fraction, while amphetamine preferentially releases the catecholamine from the particulate fraction. These results suggest that reserpine depletes norepinephrine throughout the entire neuron, initially acting on cell bodies and axons, while amphetamine preferentially releases norepinephrine from the varicosities of noradrenergic neurons.