Abstract: ObjectiveTo observe the survival and pathway of regenerative axons of spinal motoneurons following root injury of brachial plexus (BPI) and to investigate the correlation between the pathway of regenerative axons and the recovery of motor function. Methods48 adult male SD rats were randomly divided into four groups: crush group, cut group, avulsion group and the control group. 2 months later, the functional recovery was evaluated with Grooming test. Fluorogold labeled regenerative motoneurons retrogradely when injected into the motor or sensory branch of musculocutaneous nerve. 3 d later, the C_5-8 spinal cord were harvested and the regenerative motoneurons were counted. The survival neurons were counted with neutral red staining. ResultsThe number of survival neurons in the cut group (1005±89) were more than that of the avulsion group （881±76）, but less than the crush group (1126±25). The control group was the most (1900±39）. The regenerative motoneurons reinnervated motor branch were much more than that of the sensory branch in all groups. For the Grooming test, the grade in the crush group (3.42) was much higher than that of the avulsion (1.75) and cut (1.75) group. ConclusionRegenerative axons of spinal motoneurons reinnervate the motor branch after BPI. The number of survival neurons is different after different injuries, which associated with the motor functional recovery.

Key words: brachial plexus, root injury, musculocutaneous nerve, motoneurons, regeneration