Collateral sprouting from sensory and motor axons into an end to side attached nerve segment

A nerve segment, sutured end-to-side (ETS) to an intact rat sciatic nerve, becomes invaded by regenerating axons. The origin of these fibres is contro versial: it is debated whether or not they represent collateral sprouts fro m intact axons. Here we demonstrate by double retrograde tracing, using one tracer for the ETS attached segment and another for the sciatic nerve prop er double-labelled sensory neurons in 67% of the rats receiving an ETS segm ents. Double-labelled motor neurons were observed in 11% of the rats. The r esults show that a nerve segment attached ETS to an intact nerve can induce collateral sprouting of both sensory and motor axons although the extent o f such branching may vary with the experimental conditions. NeuroReport 11: 2455-2459 (C) 2000 Lippincott Williams & Wilkins.