Kinetics of glutamate (5 mM) treatment on caspase-3 protein levels in primary cortical cells. Cortical cells isolated from 19 day old fetal rat brains were cultured for 7 days and treated with 5 mM glutamate for the indicated times in a neurobasal medium containing 2% antioxidant free B27. Cells were then collected and total protein was extracted. Caspase-3 protein levels were determined by Western blot analysis as described in Figure 6. The bars depict densitometric analyses of Western blots from at least three experiments (± SEM). *P < 0.05 compared to untreated control cells.