Objective To investigate the role of p75 neurotrophin receptor（p75NTR） in the regeneration of facial nerve crush injury. Methods In p75NTR knockout mice and wild type mice, the regenerating fibres in the facial nerve were also labelled by an anterograde tracer cholera toxin B（CTB）. The next day after injury of facial nerve, CTB was injected into the trunk of the nerve in the proximal side of the crush, and then anterograde tracing and immunohistochemistry were used to examine the regeneration of axons after facial nerve crush injury. In p75NTR knockout mice and wild type mice, the facial nerves on one side were crushed and regenerating neurons in the facial nerve nucleus were labelled by Fast Blue. The facial nerve trunk was cut in the bifurcated region in the 4th day after injury and the stump was inserted into a small polymer tube containing Fast Blue. Retrograde tracing and labling motoneuron counting were used to examine the survival of motoneurons in the facial nerve nucleus after facial nerve crush injury. Results The results showed that the axonal growth of injured axons in the facial nerve of p75NTR knockout mice was significantly retarded. The umber of regenerated neurons in the facial nerve nucleus in p75NTR knockout mice was significantly reduced（P＜0.05）. Immunohistochemical staining of regenerating axons also showed the reduction in nerve regeneration in p75NTR knockout mice（P＜0.01）. Conclusion p75NTR plays an important role in the regeneration of injured peripheral nerves after injury.
