LOCALIZATION OF THE RHO-1-SUBUNIT AND RHO-2-SUBUNIT MESSENGER-RNAS IN CHICK RETINA BY IN-SITU HYBRIDIZATION PREDICTS THE EXISTENCE OF GAMMA-AMINOBUTYRIC-ACID TYPE-C RECEPTOR SUBTYPES

We have amplified partial complementary DNAs for the chicken gamma-aminobutyric acid type C (GABA(C)) receptor rho 1 and rho 2 subunits using the polymerase chain reaction. These nucleotide sequences have been utilized to design specific oligonucleotide probes for the in situ hybridization localization of the corresponding messenger RNAs (mRNAs) in the 1-day-old chick retina. Although both transcripts are found almost exclusively in the inner nuclear layer, their distributions differ markedly. From the locations of the hybridization signals, we deduce that the rho 1-subunit mRNA is present mainly in bipolar cells and that the rho 2-subunit mRNA is present in both amacrine and horizontal cells. These results suggest that the rho 1 and rho 2 subunits frequently occur in different receptor complexes and, therefore, that subtypes of the GABA(C) receptor exist.