Brain-derived neurotrophic factor (BDNF) prevents lesion-induced axonal die-back in young rat optic nerve

Lesions of the optic nerve in young animals lead to rapid retrograde degeneration of the axon stumps and to death of retinal ganglion cells. We injected different neurotrophic factors into the eye at the time of an intracranial freeze-crush lesion of the optic nerve in 8 day old rats. Optic nerve axons were visualized by anterograde tracing with wheat germ agglutinin-horseradish peroxidase (WGA-HRP) and by electron microscopy. The lesion induced a rapid die-back of the axons, which could be prevented by BDNF and to a lesser extent by neurotrophin-3 (NT-3) or ciliary neurotrophic factor (CNTF). No effect was seen in animals injected with nerve growth factor (NGF) or a mixture of acidic and basic fibroblast growth factor (FGF). In contrast to this effect on the axons, none of these factors was able to counteract the rapidly progressing degeneration of the retinal ganglion cells. These results suggest a selective influence of BDNF on the mechanisms responsible for the maintenance of optic nerve axons.