Effect of U0126 on cell viability in sympathetic neurons. Sympathetic neurons were either maintained in the presence of NGF, withdrawn from NGF or treated with U0126 (10 μM) in the presence of NGF. The cells were fixed and stained with Hoechst dye and normal and pyknotic nuclei were counted at time point 0, 24, 48 and 72 hours. (A) Example images of sympathetic neurons maintained in the presence of NGF, treated with U0126 for 72 hours or withdrawn from NGF for 72 hours. Neurons were considered viable if they retained a normal nuclear morphology. The white arrows indicate dead cells. The bar represents 10 μm. (B) Effect of U0126 on cell viability at 72 hours. The data is presented as the mean ± S.E., n = 3. Treatment with U0126 (p = 0.040) and NGF withdrawal (p = 0.0004) significantly decreases the percentage of viable neurons at 72 hours compared to the cells that were maintained in the presence of NGF.