Fig. 7.

No induction of TUNEL staining in neurons treated with the combination of camptothecin and general caspase inhibitors. Rat E18 cortical neurons were plated in poly-d-lysine-coated 35 mm dishes and treated the following day with 10 μm camptothecin alone (A, B) or in combination with zVAD-FMK (100 μm) (C, D). Twenty-four hours later, the cells were fixed and stained for TUNEL analysis (A, C), according to the manufacturer’s instructions (Boerhinger Mannheim). Nuclei were counterstained with propropidium iodide (50 ng/ml; Sigma) (B, D). Propropidium iodide and TUNEL-positive nuclei were visualized under fluorescence microscopy (magnification, 40×). The percentage of TUNEL-positive nuclei for various conditions is reported in E as the mean ± SEM (5 separate fields of at least 100 nuclei each). Scale bar, 35 μm.VAD, zVAD-FMK; Flavo, flavopiridol.