We previously showed that motor nerves are superior to sensory nerves in promoting axon regeneration after spinal root avulsion. It is, however, impractical to use motor nerves as grafts. One potential approach to enhancing axonal regeneration using sensory nerves is to deliver trophic factors to the graft. Here, we examined the regulation of receptors for brain-derived neurotrophic factor, glial cell line<derived neurotrophic factor, ciliary neurotrophic factor, and pleiotrophin after root

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... sion in adult rats. We then tested their survival-promoting and neuroregenerative effects on spinal motoneurons. The results showed that receptors for brain-derived neurotrophic factor and glial cell line<derived neurotrophic factor were upregulated and that these trophic factors promoted survival and axonal regeneration of motoneurons when they were injected into the sensory nerve graft before implantation. In contrast, receptors for ciliary neurotrophic factor and pleiotrophin were downregulated after avulsion. Ciliary neurotrophic factor did not promote survival and axonal regeneration, whereas pleiotrophin promoted axonal regeneration but not survival of injured spinal motoneurons. Our results suggest that infusion of trophic factors into sensory nerve grafts promote motoneuron survival and axonal regeneration. The technique is technically easy and is, therefore, potentially clinically applicable. http://jnen.oxfordjournals.org/ Downloaded from FIGURE 5. Insertion of a 30-gauge needle did not damage the structure of the nerve. (A) Normal untreated nerve. (B) Fixation of a nerve with the Hamilton syringe in place demonstrates a large cavity. Nerve fibers are displaced to the periphery. (C) The nerve returned to normal size and fiber distribution after 15 minutes in normal saline. (D, E) Glial cell line<derived neurotrophic factor<injected nerve after implantation into animals showed a normal distribution of remyelinated fibers. Toluidine blue<stained semithin sections. Scale bars = (AYD) 100 mm; (E) 50 Km.