LOCALIZATION OF GABA(A) RECEPTORS IN THE RABBIT RETINA

The distribution of gamma-aminobutyric acid, (GABA(A)) receptors in th e rabbit retina is investigated and compared with the distribution of GABAergic neurons using immunocytochemical methods. Antibodies against the alpha 1, beta 2/3, and gamma 2 subunits of the GABA(A) receptor l abel subpopulations of bipolar, amacrine and ganglion cells. Double la beling experiments show that the gamma 2 subunit is colocalized with t he alpha 1 and the beta 2/3 subunits in bipolar, amacrine and ganglion cells. Electron microscopy reveals that in the outer plexiform layer, GABA(A) receptor immunoreactivity is present on dendrites of cone bip olar cells adjacent to the cone pedicles. Bipolar cell dendrites are a lso receptor-positive at synapses from interplexiform cells. Some rece ptor immunoreactivity is found intracellularly in processes of horizon tal cells. In the inner plexiform layer, GABA(A) receptor immunoreacti vity is present on both rod bipolar and cone bipolar axon terminals at putative GABAergic input sites. Amacrine and ganglion cell processes in sublamina a and b are also labeled.