In vivo release of newly synthesized catecholamines from the hypothalamus by amphetamine

Summary The posterior hypothalamus of cats immobilized with gallamine was superfused through a push-pull cannula with artificial cerebrospinal fluid. Addition of³H-tyrosine into the superfusing fluid led to synthesis of³H-catecholamines which were released spontaneously. Separation of the³H-catecholamines by column chromatography or their acetylation and separation by paper chromatography revealed that both³H-noradrenaline and³H-dopamine were released. In most experiments³H-noradrenaline represented about 10 to 25% of total³H-catecholamines. Superfusion of the hypothalamus with amphetamine (1×10^–5 M) enhanced the release of total³H-catecholamines, the release of³H-noradrenaline being relatively more enhanced than that of³H-dopamine. Determination of the readioactive compounds in the hypothalamus at the end of the experiments showed that total³H-catecholamines represented 3% of³H-tyrosine. About 15% of the total³H-catecholamines were due to³H-noradrenaline and 85% to³H-dopamine.