Axonal transport of BDNF precursor in primary sensory neurons.

Recent studies have shown that the precursor of brain-derived neurotrophic factor (pro-BDNF) activates p75NTR with high affinity to induce apoptosis. Here we show that pro-BDNF is transported anterogradely and retrogradely in sensory neurons of adult rats. After a crush injury of sciatic nerves, dorsal roots or dorsal column in adult Sprague-Dawley rats, the immunoreactivity for pro-BDNF accumulated at both the proximal and distal segments. The accumulation reached a maximum at 24 h after injury. Western blot analysis also revealed pro-BDNF in sciatic nerve segments proximal and distal to the ligature and in the spinal cord. Biotinylated or Alexa-488-labelled pro-BDNF injected into sciatic nerve was internalized and transported both retrogradely and anterogradely within sensory neurons. These results demonstrate that pro-BDNF is anterogradely and retrogradely transported in sensory neurons, suggesting that endogenous pro-BDNF may be released and play important functions.