Peripheral nerve injury activates microgliacytes and astrocytes, leading to a close contact of their synapses and processes and an aberrant release of many neurotrophic factors and pro-inflammatory cytokines as brain-derived neurotrophic factor (BDNF), glia cell line-derived neurotrophic factor (GDNF), tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), interleukin-6(IL-6), etc. in the dorsal horns (DHs) of the spinal cord and brain, and thereby initiating the pain process [5, 6]. This evidence concerns the gene BDNF and peripheral nerve injury.