Figure 6. Neuroprotection due to activity-dependent suppression of Puma, Apaf-1, and Procaspase-9 expression is not via p53 inhibition. A, QRT-PCR analysis of p53 expression in p53 +/+ and +/− neurons that were stimulated as indicated for 4 h. *p < 0.05 (n = 6 +/+, n = 4 +/−). B, QRT-PCR analysis of Puma expression in p53 +/+, +/−, and −/− neurons that were stimulated as indicated. MK-801 treatment was for 24 h. BiC/4-AP treatment was for 4 h. *p < 0.05 (n = 6 +/+, n = 4 +/−, n = 4 −/−) indicates stimulus-dependent differences (n = 4). #p < 0.05 indicates differences due to genotype (i.e., compared to +/+ neurons treated in the same way). @p < 0.05 compared to level of neuronal death in BiC/4-AP-stimulated, p53 +/+ neurons. C, QRT-PCR analysis of Apaf1 and Casp9 expression in p53 +/+, +/−, and −/− neurons stimulated where indicated with BiC/4-AP for 4 h. #p < 0.05 compared to control of that particular genotype (n = 6 +/+, n = 4 +/−, n = 4 −/−). D, The neuroprotective effect of synaptic activity against staurosporine-induced apoptosis is not occluded by p53 deficiency. p53 +/+, +/−, and −/− neurons were stimulated as indicated for 16 h before the addition of staurosporine (100 nm) where indicated, for a further 24 h. After 24 h, cell death was assessed. *p < 0.05 (n = 6 +/+, n = 4 +/−, n = 4 −/−) indicates stimulus-dependent differences (n = 4). #p < 0.05 indicates differences due to genotype (i.e., compared to +/+ neurons treated in the same way). E, The neuroprotective effect of synaptic activity against trophic deprivation-induced apoptosis is not occluded by p53 deficiency. p53 +/+, +/−, and −/− neurons were stimulated as indicated for 72 h in trophically deprived medium, after which cell death was assessed. *p < 0.05 (n = 6 +/+, n = 4 +/−, n = 4 −/−) indicates stimulus-dependent differences (n = 4). #p < 0.05 indicates differences due to genotype (i.e., compared to +/+ neurons treated in the same way). There are no such differences.