Neurotrophin-3 and TrkC-immunoreactive neurons in rat dorsal root ganglia correlate by distribution and morphology

Previous studies have shown that a subpopulation of large dorsal root ganglion neurons contains neurotrophin-3 (NT3)-like immunoreactivity. It is not known, however, whether these NT3 immunoreactive neurons also express the high affinity receptor for NT3, trkC. In the present study, the distribution and morphology of trkC immunoreactive neurons have been correlated with those of NT3 immunoreactive neurons in the dorsal root ganglia. Size and segmental distributions of both antigens indicate that they are present in the same group of large sensory neurons. Almost twice the number of these neurons are present in the cervical and lumbar spinal ganglia than in the thoracic. Co- localization study indicates that 94% of NT3 immunoreactive neurons express trkC. Our findings support the proposal that NT3 in these neurons is derived from their peripheral targets rather than synthesized in situ.