Differential expression of GABA receptor subunit messenger ribonucleic acids and immunoreactivity in the rat neostriatum during postnatal development

Abstract

γ-Aminobutyric acid (GABA) is a major inhibitory neurotransmitter in the neostriatum. Functions of GABA are mediated by GABAA and GABAB receptors in the neostriatum. In order to investigate the developmental expression of GABA receptor subunits (GABAAα 1, GABAAα3 and GABAAα 6; GABAAβ2 and GABAAβ 3, and GABABR1 and GABABR 2) in the rat neostriatum, reverse transcriptase-polymerase chain reaction (RT-PCR) and immunofluorescence were performed. Tissues were obtained from rats on postnatal day (PND) 1, PND 7 and PND 14, and from adult rats. RT-PCR indicated that GABAAα1 and GABA Aα6 mRNA levels were low, but that GABA Aβ2 and GABAAβ3 mRNAs levels were high during the early postnatal period. Immunofluorescence revealed that GABAAα1 immunoreactivity was only observed in striatal interneurons in PND 14 and in adult rats. Immunoreactivity for GABAAα6 was only observed in PND 14 and adult animals. GABABR1 immunoreactivity was found to be expressed by perikarya of striatal neurons at all ages examined. In contrast, GABABR2 immunoreactivity was mainly observed in choline acetyltransferase-positive striatal interneurons in PND 14 and adult rats. The present results indicate that there are differential patterns of developmental expression of GABA receptor subunits in the neostriatum, with important implications for the development of GABA systems in rat basal ganglia. Copyright © 2008 S. Karger AG.