Effects of NOS inhibitors, Carboxy-PTIO, and Trolox on MTT reductions by primary cortical mixed cell cultures in the presence of peroxynitrite. Peroxynitrite (OONO; 100 and 200 μM) caused significant MTT reduction decreases as compared to the control (no peroxynitrite or drug exposure). The co-administration of peroxynitrite (100 μM) with Trolox at 10 (T10) or 100 μM (T100), carboxy-PTIO at 10 (C10) or 100 μM (C100), L-NIL at 100 μM (L100), or 1400W at 5 μM (W5) showed significantly higher MTT reductions than peroxynitrite treatment alone. L-NOARG at 100 μM (G100) or SMTC at 100 μM (M100) showed no significant difference in MTT reductions. Data represent mean±s.e.mean of 6–9 wells from five independent experiments. One-way ANOVA with Bonferroni's multiple comparison test and Student t-test were used to analyse statistical significance. *P<0.001 compared to peroxynitrite at 100 μM.