Short-time predegenerated peripheral nerve grafts promote regrowth of injured hippocampal neurites.

Our previous studies revealed that predegenerated peripheral nerve grafts facilitated neurite outgrowth from the injured hippocampus and that this effect was particularly distinct when 7-, 28-, and 35-days predegenerated nerve grafts were used. It is recently known that a totally transected peripheral nerve exhibits biphasic neurite-promoting activity. The early phase lasts 7 days. The aim of the present study was to find whether short-time predegenerated (1-6 days) peripheral nerve grafts exert any neurotrophic effect and when this influence is maximal. Experiments were carried out on adult male Wistar rats. Sciatic nerves were totally transected and following 1, 2, 3, 4, 5 and 6 days their distal stumps were implanted into the hippocampus. Control animals were treated with non-predegenerated sciatic nerve grafts. In all groups FITC-HRP was injected into the free end of graft six weeks following surgery. Special histochemic technique showed AChE-positive fibres inside the grafts of all examined groups. Fluorescence microscopic examination revealed the labeled cells in all examined groups, however their number was different in each group, depending on the predegeneration stage. They were most numerous at the fourth day of predegeneration.