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Yin-Peng Chen, Chuan-Chin Chiao; Functional Expression of Ionotropic Glutamate Receptors in the Rabbit Retinal Ganglion Cell. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1167.
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It has been proposed that retinal ganglion cells (RGCs) with distinct morphologies have different physiological properties. Different functions of RGCs may in part result from various expressions of N-methyl-D-aspartate (NMDA), α-amino-3-hydroxyl-5-methyliso-xazole-4-propinoic acid (AMPA), and kainic acid (KA) receptors, the major ionotropic glutamate receptor types, on their dendrites. In the present study, we aimed to characterize the functional expression of AMPA and NMDA receptors of morphologically identified RGCs in the whole mount rabbit retina.
The agmatine (AGB) activation assay was used to reveal functional expression of ionotropic glutamate receptors after the RGCs were targeted by Neurobiotin injection. Based on the result that AGB permeation patterns in RGCs depended on the agonist concentrations of AMPA or NMDA, optimal concentrations of AMPA (2 µM) and NMDA (100 µM) were selected to examine G7 and G11 types of RGCs.
We found that less than 40% of G7 type RGCs (ON-OFF direction selective ganglion cells) had salient AGB activation when incubated with 2 µM AMPA or 100 µM NMDA. The G11 type RGCs (alpha ganglion cells) also showed similar activation patterns, except that all of the OFF subtype examined had no AGB permeation under 2 µM AMPA.
These results suggest that RGCs with large somata (G7 and G11 types) may express various heterogeneous functional ionotropic glutamate receptors, which result their fast and transient responses upon light stimulation. This also implies that synaptic efficiency is much higher in some RGCs with large somata.
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