Apoptosis analyses after acute BDNF treatment after TNF-α treatment. DRG cultures were pre-treated with 5 nM TNF-α for 48 hours followed by 400 ng/ml BDNF for 10 or 40 min. Cells were immediately fixed and apoptotic cells were detected by TUNEL reaction kit. (A) Control group; (B) TNF-α-pretreated group. DNase I-treated cells served as a positive control, while reaction enzyme removal served as a negative control. TUNEL staining was detected with a fluorescent green dye and cells were counterstained with DAPI. Insert illustrates an apoptotic cell from the positive control. Scale bars, 50 μm.