Figure 4.

The NKCC1-blocking drug bumetanide prevents the posttraumatic emergence of requirement for BDNF and blocks the postaxotomy upregulation of p75^NTR. a, Bumetanide abolishes the posttraumatic cell death induction in neurons deprived of BDNF by TrkB-Fc application. n = 33 slices/3350 neurons; **p = 0.021, one-way ANOVA and Bonferroni's post hoc analyses. b, Quantification of real-time PCR analyses for p75^NTR mRNA, percentage of unlesioned control, at 1, 2, and 6 h after axotomy. At 6 h after axotomy, p75^NTR mRNA was upregulated, but not in the presence of bumetanide. n = 72 slices; ***p < 0.001, one-way ANOVA and Bonferroni's post hoc analyses. c, Fragments of representative confocal images from the CA3 region of unlesioned, lesioned, and lesioned bumetanide-treated slices stained immunohistochemically for NeuN (blue) and p75^NTR (red). Scale bar, 10 μm. d, Ratio of p75^NTR-positive neuronal number to total neuronal number, obtained by blind stereological counting in the CA3 region, percentage of unlesioned control ratio value. The amount of p75^NTR-positive neurons was increased after axotomy with and without application of TrkB-Fc; the increase is fully prevented by bumetanide. n = 53 slices/5800 neurons. **p = 0.05 (lesioned control)/0.028 (lesioned plus TrkB-Fc), one-way ANOVA and Bonferroni's post hoc analyses. e, p75^NTR is not upregulated in the lesioned slices from NKCC1 knock-out mice. Data were obtained as in d; n = 37 slices/3540 neurons. **p = 0.02, one-way ANOVA and Bonferroni's post hoc analyses. Error bars indicate SEM.