METABOLISM OF TRITIATED DOPAMINE IN REGIONS OF RAT BRAIN IN VIVO .2. SIGNIFICANCE OF NEUTRAL METABOLITES OF CATECHOLAMINES

Abstract— The levels of tritiated catecholamines and metabolites were measured in regions of the rat brain at intervals after the intraventricular injection of [3H]dopamine, [3H]nor‐adrenaline and [3H]normetanephrine. The disappearance of catecholamines and appearance of metabolites with time and the regional turnover rates of these amines indicate that the major pathway of the metabolism of noradrenaline and dopamine actively released from physiological storage sites is to the neutral alcoholic metabolites. The acid metabolites, homovanillic acid and 3,4‐dihydroxyphenylacetic acid appear to be only minor products of normal dopamine metabolism in rat brain regions including the striate, but are the main end products of the metabolism of excess exogenous dopamine. The active metabolism of stored noradrenaline to alcohol metabolites is also indicated by the increase in neutral alcohol metabolites accompanying the increased noradrenaline turnover when rats were subjected to electroshock stress. Therefore in the rat brain, neutral alcohol metabolites of dopamine and noradrenaline have great significance in the study of physiological catecholamine turnover in any region. Copyright © 1969, Wiley Blackwell. All rights reserved