FIG. 2.

Excitotoxicity and neurodegeneration. Excitoxicity results from stimulation of NMDA receptors. Calcium can flow into the cell, where it is sequestered in the mitochondria. The mitochondria's ability to buffer calcium is overwhelmed, and a decrease in membrane potential and reduction in ATP production can result, causing cytochrome c (CytC) to be released, and leading to apoptosis. Alternatively, the mitochondria may undergo the permeability transition, producing ROS, and leading to cell death by necrosis.