GABA-CONTAINING NEURONS IN THE VENTRAL TEGMENTAL AREA PROJECT TO THE NUCLEUS-ACCUMBENS IN RAT-BRAIN

The ventral tegmental area receives a gamma-aminobutyric acid (GABA) i nnervation from the nucleus accumbens and contains GABA immunoreactive neurons believed to be interneurons. We combined the immunocytochemic al detection of retrogradely transported Fluoro-Gold (FG) from the nuc leus accumbens (Acb) with the detection of GABA within the same sectio n of tissue in the ventral tegmental area (VTA) of the rat brain to de termine whether there might also be reciprocal GABAergic projections i n the mesolimbic pathway. Immunoperoxidase labeling for FG and immunog old-silver labeling for GABA were most readily distinguished within pe rikarya and dendrites in sections examined by electron microscopy. Ult rastructural observations indicated that 36% (n = 110) of the FG-label ed perikarya and dendrites also contained GABA immunoreactivity. The p resent results provide the first evidence that GABA is contained in a subpopulation of neurons in the mesolimbic pathway from the VTA to the Acb. The reciprocity of this circuitry may provide an important feedb ack loop thus facilitating inhibition of motor activity.