GROWTH OF ASCENDING SPINAL AXONS IN CNS SCAR TISSUE

The aim of the present study was to test the capacity of spinal cord s car tissue to assist and sustain axon regrowth. In adult rats and cats the dorsal funiculus (DF) was cut at mid-thoracic or lumbar level, an d a superficial incision in the DF rostral to the lesion was made in o rder to extend the penetrating lesion. Axonal tracing in rats 50-100 d ays postinjury with anterogradely transported wheatgerm agglutinin-con jugated horseradish peroxidase or rhodamine-conjugated dextran demonst rated that nerve fibers had entered the scar tissue. Axon ingrowth in the scar was further indicated by axonal immunoreactivity to the growt h-associated protein GAP-43. The scar tissue showed low-affinity neuro trophin receptor-like immunoreactivity in association with blood vesse ls and in the interstitium. The integrity of the blood-brain barrier i n the extended dorsal funiculus lesion was disrupted for at least 11 m onths postinjury, assessed by i.v. injections of free HRP or Evans blu e. The present study shows that penetrating injury in the dorsal funic ulus produces a CNS environment permissive for axonal sprouting and th at PNS influence is not necessary for spinal tract regrowth. A possibl e relationship between the absence of an intact BBB and injury-induced axonal sprouting is discussed.