Spontaneous axonal regeneration after optic nerve injury in adult rat

OPTIC nerves of adult rats were crushed 2 mm behind the eye to examine the ability of retinal ganglion cells (RGCs) to regenerate their axons. Some an imals were treated with the immunophilin ligands FK 506 or GPI 1046 for up to 4 weeks. After 10 days to 16 months, regenerating RGC axons were visuali zed using anterograde tracing and/or electron microscopy. A small proportio n of RGC axons regenerated across the lesion site and grew very slowly alon g the entire optic nerve. Immunophilin ligands had no obvious effect. The r egenerating axons were about 0.2 mu m in diameter, and usually in clusters surrounded by astrocyte processes. Thus, some CNS axons can spontaneously r egenerate long distances within degenerate white matter and this slow regen eration is not accelerated by immunophilin ligands. (C) 1999 Lippincott Wil liams & Wilkins.