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L. Heinze, S. Haverkamp, H. Wassle; Differential Distribution of Glycine Receptor Subunits on Amacrine and Ganglion Cells of the Mouse Retina . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2275.
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© ARVO (1962-2015); The Authors (2016-present)
Glycine is a major inhibitory neurotransmitter of the mammalian retina, and glycine receptors (GlyRs) are expressed at synapses from amacrine cells onto amacrine, bipolar, and ganglion cells. GlyRs are ligand gated chloride channels, composed of ligand binding α and structural ß subunits. Molecular cloning has revealed 4 genes encoding á subunits and one gene encoding the ß subunit. The properties of GlyRs vary with their subunit composition, and therefore we addressed the question whether the various types of amacrine and ganglion cells accomplish their different functions by specifically expressing different GlyRs.
Shortly fixed retinae from thy1–GFP–transgenic mice were processed for immunofluorescence double and triple labeling using specific antisera against the GlyRα1, GlyRα2 and GlyRα3 subunit. The GFP–signal was enhanced immunocytochemically, and antibodies against Calretinin were applied to define stratification levels within the inner plexiform layer.
In every thy1–GFP retina, about 10 to 50 ganglion cells and a lower number of small–field amacrine cells were GFP–labeled. 17 types of ganglion cells and 6 types of amacrine cells have been identified. We found that GlyRα1 is strongly expressed by the ganglion cell types A1, A2inner, A2outer and B1. In contrast, GlyRα2 and GlyRα3 were distributed more widely, they appear to be colocalized with several types of ganglion cells, however, they provide relatively sparse synaptic contacts with these ganglion cells. Only one amacrine cell type in our sample was associated with GlyRα1, namely the small–field, bistratified "A8" cell. In contrast, GlyRα2 is associated with all amacrine cell types described here. The same holds true for GlyRα3 with the exception of one type that only rarely colocalizes with this subunit.
Different amacrine and ganglion cells express different sets of synaptic GlyRs. Further work on the anatomical localization of GlyRs as well as electrophysiological experiments will shed light onto the specific role of the approximately 15 different glycinergic amacrine cell types and their postsynaptic partners in retinal function. Supported by SFB 269/B4
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