Semiquantitative immunocytochemical analysis of GABAA receptor subunit expression in the rat neostriatum.

A semiquantitative immunogold technique was used to investigate the levels of expression of specific GABAA receptor subunits in different regions (dorsolateral, dorsomedial and ventromedial regions) of the rat striatum. The results indicate that the subunits studied can be classified into three groups on the basis of their labelling density in the striatum: alpha 1 and alpha 3 (labelling density of less than 100 gold particles per 1000 microns2), gamma 2 and delta (between 100 and 200 particles per 1000 microns2), and alpha 2 and beta 2/3 (more than 300 particles per 1000 microns2). The alpha 1 and alpha 3 subunits are about 35% more abundant in the dorsal than in the ventral striatum, while the beta 2/3 and gamma 2 subunits are about 40% more abundant in the medial than in the lateral striatum. The alpha 2 and delta subunits did not show significant regional differences in abundance. The present data are consistent with the possibility that there are regional variations in the relative abundances of different GABAA receptor subtypes in the rat striatum.