Activation of caspase-3, after excitotoxicity in oligodendrocytes, is reduced by calpain inhibition. Oligodendrocytes were exposed to AMPA or kainate (KA) for 15 min, alone or in combination with the calpain inhibitor PD150606 (100 μm), and the total cell lysates were harvested after 4 h. Expression of procaspase-3 and active caspase-3 was assessed by Western immunoblotting using specific antibodies, and the total β-actin level was used as a control for protein loading. A, Representative blot for total procaspase-3 (top), cleaved caspase-3 (middle), and β-actin (bottom) expression obtained from oligodendrocytes treated with agonists in the absence or presence of the inhibitor PD150606. B, C, The density of the bands of procaspase-3 (B) and cleaved caspase-3 (C) was quantified using NIH Image, normalized to β-actin expression, and the values were expressed as a percentage of the bands from the untreated control (100%). The addition of AMPA or kainate to oligodendrocytes led to a decrease in total procaspase-3 (B) and an increase in active caspase-3 expression (C), which was blocked by PD150606. *p < 0.05, ***p < 0.001, compared with control cells; ^#p < 0.05, compared with cells treated with agonist alone.