compared the effects of implanting peripheral sensory nerve and motor nerve on motoneuron survival and regeneration after spinal root avulsion in adult rats. Our results showed that 116% more motoneurons regenerated axons into the motor than the sensory nerve graft and 59% of motoneurons survived in the motor nerve-implanted group compared to 48% in the sensory nerve-implanted group. We demonstrated by real time PCR that levels of BDNF and GDNF mRNA were significantly higher in the motor than the sensory nerve five days after implantation into the spinal cord. This may account for the superiority of motor over sensory nerve in promoting motor axon regeneration and motoneuron survival. Lastly, we also showed that implanting two sensory nerves enhances motoneuron regeneration over implanting a single nerve.