Abstract

The lateral and third ventricles of anesthetized cats were perfused continuously with artificial cerebrospinal fluid (CSF) containing 3H-tyrosine and the perfusate was analyzed for 3H-catecholamines. The addition of d-amphetamine sulfate to the perfusing CSF for 2 hours, beginning 2 hours after the start of the 3H-tyrosine perfusion, caused an immediate increase in the efflux of 3H-dopamine. The efflux of this amine declined subsequently despite the continued presence of amphetamine in the CSF. The addition of alpha-methyltyrosine to the CSF concurrently with the d-amphetamine did not markedly alter the immediate increase but accelerated the subsequent decline in the efflux of 3H-dopamine. This suggests that ampetamine initially releases dopamine from a "strong pool," but continuous release is dependent upon ongoing amine synthesis. The addition of d-amphetamine to the 3H-tyrosine containing CSF at the start of perfusion immediately increased the efflux of 3H-dopamine. This response was completely blocked by the presence of alpha-methyltyrosine in the CSF. Pretreatment of cats with reserpine effectively depleted the caudate nucleus of endogenous and 3H-dopamine, but did not alter the ability of d-amphetamine to increase the efflux of 3H-dopamine. Indeed, the amount of 3H-dopamine released during each collection period by either intraventricular or intravenous administration of d-amphetamine was higher than the content of the labeled amine remaining in the whole caudate nucleus. These results suggest that damphetamine can release both "stored" and "newly synthesized" 3H-dopamine from the caudate nucleus, but that the maintenance of the amphetamine-induced release of dopamine is dependent upon the newly synthetized pool.