GABA(A) RECEPTOR SUBUNITS HAVE DIFFERENTIAL DISTRIBUTIONS IN THE RAT RETINA - IN-SITU HYBRIDIZATION AND IMMUNOHISTOCHEMISTRY

The distributions of nine different subunits of the gamma-aminobutyric acid(A) (GABA(A)) receptor (alpha(1), alpha(2), alpha(3), alpha(5); b eta(1), beta(2), beta(3); gamma(2); delta) were investigated in the ra t retina using immunocytochemistry and in situ hybridization. With the exception of the alpha(5), subunit, all subunits could be localized. Each subunit was expressed in characteristic strata within the inner p lexiform layer (IPL). Some subunits (e.g., gamma(2)) showed a ubiquito us distribution, while others (e.g., delta) were restricted to narrow sublayers. Double labeling experiments using different combinations of the subunit-specific antibodies revealed colocalizations of subunits within individual neurons. Additionally, GABA(A) receptor subunits wer e mapped to distinct populations of retinal neurons by coapplication o f defined immunocytochemical markers and subunit-specific antibodies. Cholinergic amacrine cells were found to express the alpha(2), beta(1) , beta(2/3) and delta subunits, while dopaminergic amacrine cells expr ess the alpha(2), alpha(3) and gamma(2) subunits. Dissociated rod bipo lar cells express the alpha(1) and gamma(2) subunits. In summary, this study provides evidence for the existence of multiple GABA(A) recepto r subtypes in the retina. The distinct stratification pattern of the s ubunits in the IPL suggests that different functional circuits involve specific subtypes of GABA(A) receptors. (C) 1995 Wiley-Liss, Inc.