Effects of NAD+ on PARP-1-induced neuronal death. A–I, Neuronal death was induced by MNNG (A, D, G), NMDA (B, E, H), and chemical ischemia (C, F, I). Incubation times were 30 min for MNNG, 10 min for NMDA, and variable with CI. A–C, Dose–response curves are shown for each condition. NMDA-induced neuronal death was blocked by 10 μm MK801 as a positive control. Neuronal death in all three conditions was reduced by coincubation with the PARP inhibitor, DPQ (10 μm). **p < 0.01 versus control (wash only); n = 3–4. D–F show the effects of posttreatment with 1–10 mm NAD+ on neuronal death under each of the conditions shown in A–C. The NAD+ was added after washout of MNNG, CI, or NMDA. **p < 0.01 versus no added NAD+; n = 3–4. G–I show the effects of 5 mm NAD+ or 10 μm DPQ on neuronal survival when added to the culture medium at increasing time intervals after washout of MNNG, CI, or NMDA. **p < 0.01 versus no added NAD+; n = 3–4. Error bars indicate SEM.