Inhibition of caspases and AIF in Hq/Apaf1^-/- double mutants increases the survival of cortical neurons against camptothecin-induced cell death. Cortical neurons from wild-type (wt), Apaf1^-/-, Hq, and Hq/Apaf1^-/- littermates were treated with camptothecin (10 μm). Neuronal survival was measured by live/dead assay. Live cells exhibit staining for calcein-AM activity (green fluorescence), whereas dead cells stain positive for ethidium homodimer (red fluorescence). A, Neurons after 36 h of camptothecin treatment with live/dead staining. Scale bar, 100 μm. B, Quantitative analysis of survival rate measured by live/dead assay after camptothecin treatment (n = 3). C, Quantitative analysis of propidium iodide-positive (PI+) and TUNEL-positive (TUNEL+) neurons 48 h after camptothecin treatment (n = 3). ^*p < 0.01 compared with PI+.