Tumor necrosis factor-α of Red nucleus involved in the development of neuropathic allodynia.

The pro-inflammatory cytokine tumor necrosis factor-α (TNF-α) is associated with the generation of inflammatory and neuropathic pain. The current study aims to investigate the expression of TNF-α in the brain of rats with spared nerve injury (SNI), a neuropathic pain model with the lesion of common peroneal and tibial nerves. Two weeks following SNI, the immunohistochemical results identified that the expression level of TNF-α in the Red nucleus (RN) of SNI rats was apparently higher than that of sham-operated rats. To further study the roles of TNF-α in the development of neuropathic pain, different doses of anti-TNF-α antibody (20, 2.0 and 0.2 μg/ml) were microinjected into the RN contralateral to the nerve injury side of SNI rats. The results showed that the 50% paw withdrawal threshold (von Frey test) of SNI rats were increased by 20 and 2.0 μg/ml anti-TNF-α antibody as compared with that of the basic value and control groups (P<0.05), the analgesic effect lasted for 50 and 30 min, respectively. However, no significant analgesic effect was observed after 0.2 μg/ml antibody was microinjected into the RN. These results suggest that the TNF-α of RN is involved in the development of neuropathic allodynia in SNI rats.