Figure 7.

Sortilin and p75^NTR are required for the proapoptotic action of proBDNF. A, Cultured rat SCG neurons were incubated with either mature BDNF or proBDNF as indicated for 48 h. The cultures were then fixed and processed for immunohistochemistry with Tuj1 (red), followed by TUNEL analysis (green). Nuclei were counterstained with DAPI (blue). Scale bar, 100 μm. B, Replicate cultures of NGF-deprived rat SCG neurons were treated, or not, with NGF (10 ng/ml), mature BDNF (4 ng/ml), or proBDNF (4 ng/ml) in the presence or absence of 20 μm neurotensin as indicated. Forty-eight hours later, cells were processed for TUNEL analysis as in A. The percentage of TUNEL-positive neurons was scored under each culture condition. The numbers were then normalized to those neurons that were NGF deprived (varied between 10 and 20% in different experiments). Error bars indicate SEM from three independently conducted experiments. Statistical significance (p < 0.05) between each paired sample is indicated by asterisks. C, Sympathetic neurons from p75^NTR-null or wild-type (WT) mice were established as described previously (Bamji et al., 1998). Replicate cultures were treated as in B and processed for TUNEL analysis. Error bars indicate SEM from three independently conducted experiments. Statistical significance (p < 0.05) between the paired sample is indicated by asterisks.