Peripheral sciatic nerve transection injury produces a marked increase in immunoreactive NPY in rat lumbar DRG and, as a 'transganglionic' response, in their central axonal projections to the dorsal spinal cord and gracile nuclei. Local application of neurotrophin-3 (NT-3) using implanted silicone chambers applied to the proximal transected sciatic nerve stump significantly diminished the transganglionic NPY response in the gracile nucleus and spinal cord but did not affect the CGRP transganglionic response. Conversely, local application of NGF affected the transganglionic CGRP response to axotomy but did not substantially affect transganglionic gracile NPY upregulation.