Fig. 5 . Enhanced cell death after PSA removal involves the activation of p75 pathways. (A) K252a effectively blocks phosphorylation of Trk receptors. At 5 DIV, SVZ-derived neurons were exposed to BDNF (100 ng/ml) in the presence or absence of the Trk-inhibitor K252a (400 nM) and the phosphorylation state of Trk receptors was assessed by western blotting. (B) The presence of the Trk receptor blocker K252a (400 nM) does not modify the increased cell death observed in response to exogenously applied NGF (50 ng/nl) or BDNF (100 ng/ml) after PSA removal. ^*, P<0.05; ^**, P<0.001 (ANOVA, Holm-Sidak test). (C) Blocking p75-dependent pathways by inhibitors of ceramide production (10 µM fumonisin B1 and 50 nM myriocin) or c-Jun N-terminal kinase (SP600125, 20 µM) was able to prevent cell death induced by PSA removal. ^*, P<0.05 (ANOVA, Holm-Sidak test).