Figure 4.

PARP-1 activation causes a block in neuronal glycolysis that is reversed by NAD⁺. Neurons were treated with 75 μm MNNG for 30 min or 2.5 mm SIN1 for 60 min. Where used, PJ34 (200 nm) and DPQ (10 μm) were added with MNNG or SIN1. A, B, Glycolytic rate and pyruvate content were measured 1 h after MNNG or SIN1 washout. n = 3; **p < 0.001 versus control. C, D, Five millimolar NAD⁺ or 2.5 mm pyruvate was added to the after washout of MNNG or SIN1. Glycolytic rate was restored by NAD⁺, but not pyruvate, whereas intracellular pyruvate concentrations were restored by both NAD⁺, but not pyruvate. PJ34 or DPQ were given simultaneously with MNNG or SIN1. n = 3; **p < 0.001 versus no posttreatment (white bar). E, F, ATP and AMP were measured 1 h after MNNG or SIN1 washout. The effects of MNNG on ATP and AMP levels were blocked by cotreatment with PJ34 or DPQ, and also blocked by posttreatment with NAD⁺ or pyruvate. Error bars indicate SEM.