[The influence of treatment with cocaine on the synthesis and liberation of cerebral noradrenaline].

The influence of cocaine (10 mg/kg, i.m.) on the synthesis and the release of noradrenaline (NA) has been studied in rat brain. Cocaine pretreatment reduced significantly the amount of NA-3H synthetized from tyrosine-3H (TY-3H) in the whole brain and various cerebral structures. The synthesis rates of NA (estimated by calculation of the ratio: amount of NA-3H/tissular specific activity of TY-3H) were reduced by 40% in the whole brain, 30 and 60 min after administration of TY-3H. The rise of the NA endogenous level 10 min after administration of a monamine oxidase inhibitor (ranylcypromine) was inhibited after cocaine treatment. The release of NA has been studied after inhibition of its synthesis by alpha-methyl-paratyrosine. Cocaine pretreatment significantly delayed the disappearance rate of cerebral NA. The possible mechanisms by which cocaine reduced NA turnover are discussed.