Expression profiling of GABAA receptor beta-subunits in the rat retina

This study profiled the expression of the family of GABAA receptor beta-subunits in the adult rat retina. Using a combination of reverse transcriptase reaction followed by polymerase chain reaction (RT-PCR) with gene-specific primers, the expression of mRNAs encoding the beta 1, beta 2, and beta 3 subunits was first examined in the intact retina and then in separated retinal nuclear layers. However, it was found that a critical analysis had to be carried out at the level of the single cell in order to resolve the differential patterns of expression among the retinal cell types. When cells were isolated and identified following acute dissociation, RT-PCR revealed that individual rod photoreceptor cells expressed consistently the beta 1 and beta 2 messages while the bipolar cells expressed the beta 1 and beta 3 messages. Ganglion cells displayed considerable variability in beta-subunit expression, perhaps reflecting their functional and morphological heterogeneity in the retina. In contrast, the nonneuronal Mueller cells did not express any of the beta-subunit messages. These results indicate that the expression of GABAA receptor subunits is cell-type dependent. Furthermore, as the expression of other families of GABAA receptor subunits are profiled and the patterns of subunit assembly are better understood, our results raise the possibility that GABAA receptors with different subunit compositions can be expected to be coexpressed within a single retinal neuron.