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E. Ivanova, U. Muller, H. Wassle; Evaluation of the Glycinergic Input of Mouse Bipolar Cells . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1189.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Glycine and GABA are the major inhibitory transmitters of the mammalian retina. Bipolar cells have glycine receptors (GlyRs) at their axons and glycine is supplied by multiple types of narrow–field amacrine cells. Here we evaluated the functional properties of glycine receptors in bipolar cells. Methods: Patch–clamp recordings were performed on retinal slices in wild type and Glra3(–/–) mice. Whole cell currents following glycine application and spontaneous inhibitory postsynaptic currents (sIPSCs) were measured. Several bipolar cell types were prelabeled, either by expression of GFP (GUS8.4GFP mice) or by immunostaining with selective antibodies. During the recordings the cells were filled with Alexa488 and after the experiments using calretinin immunostaining they were unequivocally identified. Results: Glycine induced currents of bipolar cells were not picrotoxinin sensitive and thus represent heterooligomeric channels composed of α and ß subunits. All OFF–cone bipolar cells showed large glycine induced currents and the analysis of sIPSCs showed that they were mediated through channels containing GlyRα1 and GlyRα3 subunits. In contrast, we did not observe glycinergic sIPSCs in ON–cone bipolar cells and could elicit only small, if any, glycinergic currents. Rod bipolar (RB) cells showed prominent glycine induced currents and these were mediated preferentially through GlyRα3 containing channels in wild type animals. In RB cells of Glra3(–/–) mice GlyRα1 subunits appear to be upregulated and we found predominantly α1 expressing channels. Conclusions: In wild type animals, OFF–cone bipolar cells receive a prominent glycinergic input, from AII amacrine cells, which is mediated preferentially through fast GlyRα1 containing channels. RB cells also receive a moderate glycinergic input through slower GlyRα3 expressing channels. ON–cone bipolar cells express very few or no glycine receptors. In Glra3(–/–) mice, there appears to be an upregulation of the GlyRα1 subunits.
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