Cortical cell cultures were pre-incubated (32 h) with varying doses (0 – 300 μM) of acetaminophen (APAP) for 32 h. The cells were challenged with either menadione (5 μM) (Fig. 2a) or H2O2 (500 μM) (Fig. 2b) for 4 h and cell viability evaluated by MTT assay. Data are mean ± SD from 3 separate experiments. **p < 0.01 vs. menadione alone; ***p < 0.001 vs. menadione or H2O2 alone; #p < 0.001 vs. control.