Expression patterns of the GABA(A) receptor α1-,β2-,γ2- and γ4-subunit genes in chick retina

We have investigated the locations of the GABA(A) receptor α1-, β2-, γ2- and γ4-subunit mRNAs, in chick retina, by in situ hybridization. The α1-, β2- and γ2-subunit genes were chosen for study because they are co-expressed throughout the mammalian and avian brain. The γ4-polypeptide gene was selected because it is highly expressed, in the chick brain, in those regions that are involved in the processing of visual information. We find that the α1-, β2- and γ2-subunit mRNAs are present in both the inner nuclear layer (INL) and the ganglion cell layer (GCL); however, the distributions of the three transcripts in these two layers show significant differences. In contrast, the γ4-polypeptide mRNA is only detected in the inner portion of the INL. These results strongly suggest the existence of multiple GABA(A) receptor subtypes in chick retina