We have previously shown that a lumbosacral ventral root avulsion leads to a progressive autonomic and motor neuron death in an adult rat model of cauda equina injury (Hoang et al., JCN, 2003). However, implantation of the avulsed ventral root into the spinal cord can protect these neurons against cell death and promote reinnervation of the implanted avulsed ventral root (Hoang et al., SfN abstract 76.15, 2003). Here, we studied some of the regenerative aspects of this injury and neural repair strategy in the adult rat at 6 weeks to 5 months postoperatively. We performed a unilateral L5-S2 ventral root avulsion injury with and without an acute implantation of the avulsed L6 ventral root into the spinal cord. Using immunohistochemistry for choline acetyltransferase (ChAT), we demonstrated several unusual and aberrant ChAT positive structures with an axonal phenotype. These structures exhibited a uniform diameter, an irregular course, occasional branching, and large terminal bouton-like swellings in the whit...