[Pharmacological modulation of dopaminergic transmission in the rat striatum in vivo].

Inhibition of catechol-0-methyltransferase (COMT) activity by Tolcapone was shown to result in increase of the striatal DA extracellular content in unrestrained rats pretreated with L-3,4-dihydroxyphenilalanine combined with Carbidopa, the decarboxylation inhibiting agent. Tolcapone enhanced the increase of the DA level in the rat striatal dialysates produced by treatment of these animals with specific DA re-uptake blocker GBR 12909. The latter elicits stereotype behaviour in rats that is substantially enhanced by tolcapone. The DA turnover rate in the striatum was decreased by the GBR 12909. The data obtained suggest that the DA transporter of neuronal membrane plays a major role in the neurochemical homeostasis at synaptic level.