The effect of Anti-NGF receptor (p75 Neurotrophin Receptor) antibodies on nociceptive behavior and activation of spinal microglia in the rat brachial plexus avulsion model.

Study Design: We measured the response of the behavior and spinal glial activation to anti-nerve growth factor receptor (p75 neurotrophin receptor [p75NTR]) antibodies in the rat brachial plexus avulsion (BPA) model.
Objective: The aim of this study was to investigate the effect of anti-p75NTR antibodies on nociceptive behavior and activation of spinal microglia in the rat BPA model.
Summary of Background Data: Tanezumab (anti-nerve growth factor antibody) treatment is associated with pain reduction and improvement in function, but with several complications.
Methods: Thirty male Wistar rats were used. In the BPA group, the C8-T1 roots were avulsed from the spinal cord with forceps at the lower trunk level and 10 μL of saline was applied locally (n = 10). In the anti-p75NTR group, the C8-T1 roots were avulsed and 10 μL of anti-p75NTR antibody was applied locally (n = 10). In a sham-operated group, the lower trunk was simply exposed (n = 10). Mechanical hyperalgesia and pain-induced walking patterns were measured using von Frey filaments (Stoelting, Wood Dale, IL) and the CatWalk gait analysis (Noldus Information Technology, the Netherlands) system every third day for 3 weeks. Activation of astrocytes and microglia was immunohistochemically examined in the spinal cord using anti-glial fibrillary acidic protein (GFAP) and anti-Iba1 antibodies both 7 and 21 days after surgery.
Results: Animals in the BPA group displayed significant mechanical hyperalgesia that continued through day 21 compared with animals in the sham-operated group, and mechanical hyperalgesia in the anti-p75NTR group was significantly improved 6 days after the operation. Regarding pain-induced gait analysis via CatWalk, animals in the BPA group displayed a significantly greater pain-like gait pattern than the p75 group for up to 3 weeks. Levels of GFAP-immunoreactive astrocytes and Iba1-immunoreactive microglia in the anti-p75NTR group were significantly reduced compared with the BPA group.
Conclusion: Our results suggest that p75NTR contributes to neuropathic pain associated with BPA, and that inhibition of p75NTR reduces neuropathic pain.
Level of Evidence: N/A.