AbstractThis study profiled the expression of the family of GABA_A receptor β-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 β₁, β₂, and β₃ 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 β₁ and β₂ messages while the bipolar cells expressed the β₁ and β₃ messages. Ganglion cells displayed considerable variability in β-subunit expression, perhaps reflecting their functional and morphological heterogeneity in the retina. In contrast, the nonneuronal Mueller cells did not express any of the β-subunit messages. These results indicate that the expression of GABA_A receptor subunits is cell-type dependent. Furthermore, as the expression of other families of GABA_A receptor subunits are profiled and the patterns of subunit assembly are better understood, our results raise the possibility that GABA_A receptors with different subunit compositions can be expected to be coexpressed within a single retinal neuron.