Glutamate-dependent toxicity in HT-22 cells is concentration dependent. HT-22 was treated with the indicated concentrations of glutamate and cell viability assessed with MTT assay. Cells exposed to glutamate concentrations greater than 2.5 mM showed significant decrease in cellular viability. Glutamate exhibited a LD50 of 3.0 mM in HT-22 (inset). Values represent the means ± SD as a percent (%) of control (*p<0.05, ***p<0.001).