In vivo characterization of basal amino acid levels in subregions of the rat nucleus accumbens: effect of a dopamine D-3/D-2 agonist

Recent evidence demonstrates that two subdivisions of the nucleus accumbens , the dorsolateral core and the ventromedial shell can be distinguished by morphological, immunohistochemical and chemoarchitectural differences. In t he present study, we measured basal levels of amino acids in microdialysate s from both the shell and core subterritories of the nucleus accumbens in f reely moving rats using HPLC with fluorescence detection. The effect of the dopamine D-3/D-2 receptor agonist quinelorane (30 mug/kg s.c.) was then in vestigated in both subregions. With the exception of glutamate, histidine, and serine, which showed similar levels in both subterritories, alanine, ar ginine, aspartate, gamma -aminobutyric acid, glutamine, and tyrosine were s ignificantly higher in the shell compared with the core. In contrast, tauri ne levels were significantly lower in the shell than in the core. A particu larly striking difference across subregions of the nucleus accumbens was ob served for basal GABA levels with a shell/core ratio of 18.5. Among all the amino acids investigated in the present study, quinelorane selectively dec reased dialysate GABA levels in the core subregion of the nucleus accumbens . The results of the present study point to specific profiles of both shell and core in terms of(1) basal chemical neuroanatomical markers for amino a cids; and (2) GABAergic response to the DA D-3/D-2 agonist quinelorane. (C) 2001 Elsevier Science Ltd. All rights reserved.