Aβ induced the intracellular level of superoxide anion (SOA) in microglial cells: effects of NAC and PDTC. Nitro blue tetrazolium (NBT) to formazan by superoxide anion (O2-) was used to measure the production of SOA. (A) BV-2 cells were pretreated with NAC (5 mM) or PDTC (20 μM) for 1 h and then stimulated with oligomeric Aβ(1-42) (1.0 μM) or fibrillar Aβ(1-42) (5.0 μM) for 12 h. Treatment of cells with t-BHP (100 μM) alone for 1 h was as a positive model control. Then NBT was incubated for a further 45 min and was fixed with methanol. The cells containing blue formazan particles (NBT-positive cells) were visualized under the microscope. (a): Blank (without NBT incubation); (b): Drug-free groups; (c): t-BHP alone; (d): oAβ alone; (e): NAC+oAβ; (f): PDTC+oAβ; (g): fAβ alone; (h): NAC+fAβ; (i): PDTC+fAβ. Scale bar = 50 μm. (B) NBT depositing inside the cells were dissolved with solubilization solution and the superoxide anion levels were quantified by the absorbance measured on a microplate reader at 630 nm. Each value is expressed as mean ± S.E. ###P < 0.001, compared with the drug-free group. **P < 0.01, compared between groups.