IMMUNOCYTOCHEMICAL LOCALIZATION OF THE GABA(C) RECEPTOR RHO-SUBUNITS IN THE MAMMALIAN RETINA

Polyclonal antibodies against the N terminus of the rat pi subunit wer e generated to study the distribution of GABA(C) receptors in the mamm alian retina. The specificity of the antibodies was tested in Western blots and transfected HEK-293 cells. No cross-reactivity with the GABA (A) receptor subunits alpha 1-3, beta 1-3, gamma 2, delta or with the glycine receptor subunits alpha 1 and beta could be detected. In contr ast, the rho 1, rho 2, and rho 3 subunits were all recognized by the a ntibodies. In vertical sections of rat, rabbit, cat, and macaque monke y retinae, strong punctate immunoreactivity was present in the inner p lexiform layer. Weaker immunoreactivity was also present in the outer plexiform layer, and cell bodies of bipolar cells were faintly labeled . Double immunostaining of vertical sections and immunostaining of dis sociated rat retinae showed the punctate immunofluorescence to colocal ize with bipolar cell axon terminals. The puncta possibly represent cl ustering of the rho subunits at postsynaptic sites.