Temporal mRNA expression of BDNF (a), GDNF (b), CNTF (c), NGF (d), and NT-3 (e) in distal nerve stump after tibial nerve transection. C, control; IR, immediate repair; D, denervated, SP, sensory protected. Asterisks (*) placed directly above standard error bars indicate a significant difference between a particular operated group and control at this time point (p < 0.05). Significant differences between other groups are indicated by bars. Error bars represent SEM.