TRKB-LIKE IMMUNOREACTIVITY IN RAT DORSAL-ROOT GANGLIA FOLLOWING SCIATIC-NERVE INJURY

The expression of full-length trkB protein, the functional high affini ty receptor for BDNF and NT-4, was examined by immunohistochemistry in adult rat L4-L5 dorsal root ganglia after different types of sciatic nerve lesions. In normal ganglia, 52.5% of the neurons showed trkB-lik e immunoreactivity. Size measurements demonstrated that trkB-like immu noreactivity was seen predominantly in small- and medium-sized cells. This was confirmed by the finding that 28% of all trkB-positive neuron s showed affinity to RT97, an antibody which labels a neurofilament ep itope specific for medium-sized and large primary afferent neurons. Af ter crush, section or neuroma formation of the sciatic nerve, the prop ortion of trkB-positive cells was 64.5%, 58% and 61.9%, respectively. Since trkB-receptors are present in regenerating primary afferent neur ons, these data could indicate that BDNF and/or NT-4 are involved in s ensory nerve fiber regeneration after adult injury.