Expression of GABA transaminase immunoreactivity in interneurons of the rat neostriatum

Immunoreactivity for gamma-aminobutyric acid transaminase (GABA-T), a degradation enzyme for GABA, was localized by immunocytochemistry in the rat neostriatum and the globus pallidus using a monoclonal antibody. Immunoreactivity for GABA-T was found primarily in interneurons and in the neuropilar elements in the neostriatum. Many of GABA-T-immunoreactive neurons were found to display parvalbumin immunoreactivity. This indicates many of the GABA-T-immunoreactive neurons are striatal GABAergic interneurons. Occasionally, GABA-T-immunoreactive glial cells were found. In the globus pallidus, many pallidal neurons also displayed GABA-T immunoreactivity and many of the immunoreactive neurons were seen to express parvalbumin immunoreactivity. Immunoreactivity for GABA-T was also detected in the neuropil of the globus pallidus. The present results indicate the GABAergic interneurons in the neostriatum and a subpopulation of pallidal neurons play an important role in metabolic degradation of GABA in the basal ganglia.