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M. Watanabe, H. Kudo, T. Nakazawa, M. Tamai; Survival Difference in Type and Function of Retinal Ganglion Cells Against NMDA Toxicity in Adult Cats. Invest. Ophthalmol. Vis. Sci. 2007;48(13):639.
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© ARVO (1962-2015); The Authors (2016-present)
To examine difference in survival of retinal ganglion cell (RGC) type and function against NMDA toxicity in the cat retina and to compare the results after optic nerve (OpN) transection since OFF-RGCs are vulnerable to axotomy (Yata et al., ARVO 2006).
RGCs were labeled with massive injections of DiI into the optic tracts. A week later NMDA in 10 micro L saline was injected into the left eye at 0.2 mM to 0.8 mM intraocular end density. The left and right retinae were dissected at day 14 for Lucifer Yellow (LY) injections. To recognize the border between the IPL and INL, processes of dopamine amacrine cells were immunostained with anti-tyrosine hydroxylase antibody. Dendritic depth of RGCs was determined by Neurolucida analysis in flat-mounted retinae to know whether the RGCs were ON or OFF: OFF-RGCs spread dendrites in the sublamina a of IPL, ON-RGCs in the sublamina b of IPL, respectively.
Mean ratio of the number of surviving retinal ganglion cells (RGCs) in NMDA-injected retina versus that in the paired intact retina reduced from 59.4% (0.2 mM) to 14.1% (0.8 mM) at day 14. According to reduction of the ratio and number of surviving RGCs, ratios of large cells, possible alpha cells, increased from 1.38 to 3.60, indicating resistance of alpha cells at higher NMDA. Proportion of each cell type, alpha, beta or not alpha/beta cell, was obtained with Lucifer yellow injections and ratios of the types in experiment and control retinae were obtained. Survival ratios (left retina/right retina) of alpha cells gradually decreased from 56% at 0.2 mM to 19% at 80 mM while those of beta cells decreased from 75% at 0.2 mM to 9.9% at 0.8 mM. Although OFF-RGCs are vulnerable to axotomy (Yata et al., 2006), ratios of ON-RGCs versus OFF-RGCs in 0.6 mM NMDA were not different from those in the intact retinas, indicating ON- and OFF-RGCs were equally vulnerable.
As in vulnerability to axotomy, beta cells were vulnerable at higher NMDA concentration. No difference in survival between ON- and OFF- RGCs suggeting that neuronal death after OpN transection may not be related with NMDA receptor pathway in cat RGCs.
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