The levels of BDNF in L1 mice are not sufficient for spinal sensitization. (A) Time course for ventral root responses to a series of A-fiber intensity stimuli, before and after C-fiber specific conditioning (200 μA, 200 μs at 2 Hz). Data were obtained from spinal cords of wild type (wt) (n = 6), BDNF+/- (n = 3) and BDNF-/- (n = 5) mice. In the BDNF+/- group, DR-VRRs were larger in the 2 h postconditioning compared to the preconditioning period (One-way ANOVA, Bonferroni post-test, P < 0.05). In the BDNF-/- group the conditioning stimulus failed to modify DR-VRRs. (B and C) Ventral root responses by graded stimuli applied to the dorsal root before and after prolonged superfusion of exogenous BDNF, obtained from wild type (wt) (n = 5) and L1 (n = 6) mice. (D) BDNF mRNA levels in DRG were measured by quantitative PCR before, 3 and 5 days after intraplantar injection of complete Freund's adjuvant in wild type (wt) (n = 6) and L1 (n = 6) adult mice. The mRNA levels are expressed as ratio to HPRT mRNA levels. * Refers to comparison with wild type and # refers to comparison with day 0. Statistically significant differences between groups were measured by One-way ANOVA with Bonferroni post-test. *** and ###, P < 0.001. (E) BDNF protein levels in lumbar spinal cord 36 h after intraplantar injection of saline or complete Freund's adjuvant in wild type (wt) (n = 3+3) and L1 (n = 3+3) adult mice. Pools of the three mice in each experimental group were analyzed. The immunoreactive bands and densitometry quantification are shown. BDNF values were corrected by β-actin levels.