AbstractUsing patch-clamp recording in combination with reverse transcriptase-polymerase chain reaction (RT-PCR), we show in individual bipolar cells acutely dissociated from the adult rat retina a correlation between the expression of the GABA_A receptor ρ1 subunit mRNA and a bicuculline-resistant, diazepam-insensitive component of the GABA-activated whole-cell current response. This “GABA_C-like” response, contributing to approximately 42% of the GABA-activated whole-cell current and displaying variable sensitivity to picrotoxin, was found in bipolar cells but not in any of the ganglion cells examined. Expression profiling of GABA_A receptor subunit mRNAs in individual electrophysiologically tested retinal neurons revealed that, while both bipolar cells and ganglion cells may express numerous GABA_A receptor subunit isoforms, including that of ρ2, the expression of the ρ1 subunit was strictly limited to bipolar cells. We propose a possible link between the presence of a receptor with GABA_C-like pharmacological profile and the expression of the retina-specific ρ1 subunit isoform. The results presented in this study constitute the first direct demonstration of such a correlation at the single-cell level.