GABA-A RECEPTORS CONTAINING ALPHA-1 AND BETA-2 SUBUNITS ARE MAINLY LOCALIZED ON NEURONS IN THE VENTRAL PALLIDUM

The gamma-aminobutyric acid (GABA) projection from the nucleus accumbens to the ventral pallidum (VP) is important in the regulation of locomotion. Thus, stimulation and inhibition of GABA(A) receptors in the VP can alter locomotor activity. To determine whether the GABA(A) receptors are located presynaptically on accumbens efferents to the VP or postsynaptically on neurons intrinsic to the VP two experiments were performed. In the first, quinolinic acid lesions of the nucleus accumbens did not alter [H-3]muscimol binding in the VP, while lesions in the VP significantly reduced (60-80%) binding as measured by light microscopic receptor autoradiography. In the second experiment, in situ hybridization with oligonucleotide probes for mRNAs of the alpha-1 and beta-2 subunits of the GABA(A) receptor was examined in the nucleus accumbens and VP. No mRNA for either subunit was observed in the nucleus accumbens, although many positively labeled neurons were present within the VP. By contrast, a moderate to high density of cells in both the nucleus accumbens and VP contained mRNA for glutamic acid decarboxylse. These data argue that the majority of GABA(A) receptors in the VP are not located presynaptically on axonal terminals originating from neurons in the nucleus accumbens.