Letter to :J&-uroscience - Anatomical Neuropharmacology Unit

Subcellular localization of GABA" receptor subunits 743# rat-(32/3 "t ~; rat-a6rnlrnlrnlFig. 2also immunoreactive and immunoreactivity was presentat the extracellular face of the granule cellplasma membrane, demonstrating extracellular epitopes.The reaction was present all around the granulecell dendrites including the synaptic cleft of theGolgi cell terminals. The granule cell somatic membranewas also immunopositive for both the rx 1 andf32/3 subunits. As previously described, peroxidaseend-product was present between the membranesof neighbouring granule cell bodies, although theyreceived no synapses. J8 This was in contrast to peroxidasereaction end-product observed after using antiserumto the rx6 subunit. In the latter case only rarelywere small patches of peroxidase reaction productdetected in the somata of granule cells. This labellingwas present in all layers and in all cells and was aresult of background staining in the avidin biotinylatedhorseradish peroxidase complex (ABC) procedure.Immunoreactivity could not be observed inany axon terminal, Golgi or glial cells for any of thesubunits studied here.Distribution of immunoreactivity for the rx 6 sub unit incomparison with in situ hybridization and receptorbindingUsing an antiserum specific for the rx6 subunit ofthe GABA A receptor, the subunit is found restrictedto the dendrites of the granule cells. This correlateswell with the expression of the mRNA coding for therx6 subunit in the granule cellsY·15 The selectivelocalization of immunoreactivity to granule cells ofthe cerebellum also confirms the specificity of the