trk immunoreactivity at neuronal dendrite and cell body.

Neurotrophins homologous to the nerve growth factor (NGF) bind the neurotrophic receptors of the trk gene family. Since the target tissues release these neurotrophic factors to the neuron, it has been believed that their trophic effects are mediated by the retrograde axonal transport. However it remains an open question whether the neurotrophins act through the autocrine or the paracrine mechanisms, since the protein-level expression of trk has not been studied so far. We have made polyclonal antibodies against the recombinant proteins of chicken trkC and rat trkB. These antibodies showed immunoreactivity at the dendrite and the cell body of neuron. This subcellular localization strongly suggests the autocrine or the paracrine mechanism of the neurotrophic factors. At the same time, our data provide basic knowledge to decide where to deliver these neurotrophic factors in the therapy of neurodegenerative diseases.