GABAAReceptor subunits have differential distributions in the rat retinae: In situ hybridization and immunohistochemistry

Abstract

The distributions of nine different subunits of the gamma‐aminobutyric acid_A (GABA_A) receptor (α₁, α₂, α₃, ₅; β₁, β₂, β₃; γ₂; δ) were investigated in the rat retina using immunocytochemistry and in situ hybridization. With the exception of the α₅ subunit, all subunits could be localized. Each subunit was expressed in characteristic strata within the inner plexiform layer (IPL). Some subunits (e.g., γ₂) showed a ubiquitous distribution, while others (e.g., δ) 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 were mapped to distinct populations of retinal neurons by coapplication of defined immunocytochemical markers and subunit‐specific antibodies. Cholinergic amacrine cells were found to express the α₂, β1, β_2/3 and δ subunits, while dopaminergic amacrine cells express the α₂, α₃ and γ₂ subunits. Dissociated rod bipolar cells express the γ₂ subunits. In summary, this study provides evidence for the existence of multiple GABA_A receptor subtypes in the retina. The distinct stratification pattern of the subunits in the IPL suggests that different functional circuits involve specific subtypes of GABAA receptors.