Susceptibility of retinal ganglion cells to excitotoxicity depends on somasize and retinal eccentricity

Purpose. This study was undertaken to determine if retinal ganglion cell se nsitivity to intraocular N-methyl-D-aspartate or kainate injections varied as a function of retinal location (eccentricity) or cell soma size. Methods. Rat retinal ganglion cells surviving intraocular N-methyl-D-aspart ate or intraocular kainate induced lesions were retrogradely labeled with h orseradish peroxidase and analyzed using an image analysis system. Control animals were retrogradely labeled after vehicle injection only. Cell counti ng was performed at 48 sampling points over the entire retina and represent ed a total area of 1.92 mm(2) per retina. Results. Larger cells were more sensitive to kainate than to N-methyl-D-asp artate excitotoxicity; smaller cells more vulnerable to N-methyl-D-aspartat e excitotoxicity. Further from the optic nerve, more smaller cells survived kainate administration. After N-methyl-D-aspartate administration, larger cells survived most, noticeably in the central retina. Conclusions. Our results suggest that loss of retinal ganglion cells after N-methyl-D-aspartate or kainate administration affects distinct populations of retinal ganglion cells, dependent upon soma size and retinal location. The mechanism by which certain classes of cells survive or succumb to such insults has yet to be determined.