ENDOGENOUS NEUROTROPHIN-3 IS RETROGRADELY TRANSPORTED IN THE RAT SCIATIC-NERVE

To address the active transport of neurotrophins, nerve growth factor, brain-derived neurotrophic factor, and neurotrophin-3 in the peripher al nerves, we examined the levels of proteins and messenger RNAs in th e sciatic nerve of adult rats following transection, using enzyme immu noassays and reverse transcription polymerase chain reaction method, r espectively, Neurotrophin-3 protein increased one day after transectio n only in the distal segment next to the transection site and returned to the original level two days later, This mas considered to reflect accumulation of neurotrophin-3 transported from the periphery toward t he neuronal cell bodies, because the neurotrophin-3 messenger RNA leve l was not changed in any sciatic segments during this experimental per iod. An increase in brain-derived neurotrophic factor protein was obse rved simultaneously in both the distal and proximal stumps three days after transection. Brain-derived neurotrophic factor messenger RNA was elevated in the same stumps two days after transection, suggesting th at brain-derived neurotrophic factor Has produced within the transecte d stumps. These observations demonstrate that neurotrophin-3, like ner ve growth factor, is retrogradely transported in the sciatic nerve but that brain-derived neurotrophic factor is not. This suggests that neu rotrophin-3 plays a role in the conveyance of trophic signals from tar get organs to neurons. (C) 1998 IBRO, Published by Elsevier Science Lt d.