Excitotoxicity as a Stimulus for Neuronal Cell Death

There is considerable evidence that overstimulation of glutamate receptors promotes cell death in a number of retinal disease processes. Glutamate overstimulation may be particularly important in acute ischemic injuries, but it also may play a role in diabetic retinopathy (16) and chronic neurodegenerative processes such as glaucoma (17). Evidence for this includes the observation that glutamate levels are elevated in the vitreous of patients with these conditions (16,17). 

Retinal ischemic injury, for example, has been shown to result in the overstimulation of ionotropic glutamate receptors following the extracellular accumulation of glutamate (18,19). This effect appears to involve, in particular, the NMDA class of glutamate receptors. The subsequent excessive influx of calcium results in 

Ionotropic glutamate receptors Metabotropic glutamate receptors 

NMDA AMPA Kainate Class 1 Class II Class III 

NR2B GluR2 GluR6 mGluRI KA1 mGluR2 mGluR4 

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