Involvement of glutamate in ischemic neurodegeneration in isolated retina.

Retinal ischemia, a major cause of visual loss, is believed to result from overexcitation of glutamate receptors. However, under euglycemic and normoxic conditions, exogenously applied glutamate is not neurotoxic in the retina. Under such conditions, exogenous glutamate typically causes glia swelling and requires very high concentrations to produce neurotoxicity.

Glutamate transporters and retinal excitotoxicity.

Glutamate appears to play a major role in several degenerative retinal disorders. However, exogenous glutamate is only weakly toxic to the retina when glutamate transporters on Müller glial cells are operational. In an ex vivo rat retinal preparation, we previously found that exogenous glutamate causes Müller cell swelling but does not trigger excitotoxic neurodegeneration unless very high concentrations that overwhelm the capacity of glutamate transporters are administered.