LOCALIZATION OF THE RHO-1-SUBUNIT AND RHO-2-SUBUNIT MESSENGER-RNAS INCHICK 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-ami nobutyric acid type C (GABA(C)) receptor rho 1 and rho 2 subunits usin g the polymerase chain reaction. These nucleotide sequences have been utilized to design specific oligonucleotide probes for the in situ hyb ridization localization of the corresponding messenger RNAs (mRNAs) in the 1-day-old chick retina. Although both transcripts are found almos t exclusively in the inner nuclear layer, their distributions differ m arkedly. From the locations of the hybridization signals, we deduce th at 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 cell s. 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.