Long-term survival of peripheral axons that have reinnervated the spinal cord

Adult cats received grafts after the fashion of Barnes and Worall by anastomosing the central stump of a ventral L7 root to the central stump of a dorsal L6 root. After regeneration periods from 4 weeks to 316 weeks (79 months) the regenerated axons were identified by the horseradish peroxidase technique. In some animals, regenerated boutons were identified using electron microscopy. With shorter regeneration times, most of the labeled axons were seen in the white matter of the dorsal funiculus. In the longest surviving cat, labeled axons were seen in the entire medial half of the dorsal horn grey matter. Boutons derived from regenerated axons appeared typical of CNS boutons, showing none of the morphologic characteristics of the motor end plate.