No abstract

The rat ventral tegmentum (containing dendrites and somata of mesolimbic neurones) contained 1.3 pglg of dopamine, which was reduced to 40% of the control level by reserpine. Slices of ventral tegmentum were able to accumulate and release (elevated potassium or protoveratrine A) exogenous [3H]dopamine. In parallel studies the uptake mechanism in ventral tegmentum w a s shown t o be virtually identical t o t h e nerve terminal uptake of ["Hldopamine by slices of nucleus accumbens. The release of [RH]dopamine was indistinguishable from that observed in substantia nigra, where there is substantial evidence for dendritic mechanisms. Basal adenylate cyclase activity was present, but dopamine-stimulated activity was not detected. A high GABA concentration (7.7 pmolig) was present in ventral tegmentum, in conjunction with an uptake and a release mechanism for [3H]GABA. GABA and muscimol elicited a small, reproducible efflux of [3H]dopamine, but an interaction between dopamine and [JH]GABA efflux was not observed. The results are in accord with transmitter roles for dopamine and GABA in the somatodendritic area of mesolimbic dopaminergic neurons.Address reprint requests to Dr. P. M. Beart.Abbreviation3 used: DA, Dopamine: DOPAC, 3,4-dihydroxyphenylacetic acid; GABA, y-Aminobutyric acid.