Using
laser-induced photoactivation of intravenously administered
rose Bengal in rats, we generated an ischemic
infarction of the intrascleral portion of the optic nerve (ON) comparable to that which occurs in humans to investigate optic nerve axon degenerative events following optic nerve
infarct and the potential for axon re-growth. Animals were euthanized at different times post
infarct. Axon degeneration was evaluated with SMI312 immunolabeling, and
GAP-43 immunostaining was used to identify axon regeneration. Terminal dUTP nick end labeling (TUNEL) was used to evaluate retinal ganglion cell (RGC) death. There was significant axon structural disruptinot ion at the anterior intrascleral portion of the ON by 3d post-
infarct, extending to the posterior ON by 7d post-
stroke. Destruction of normal axon structure and massive loss of axon fibers occurred by 2 weeks.
GAP-43 immunoreactivity occurred in the anterior ON by 7d post-
infarct, lasting 3-4 weeks, without extension past the primary ischemic lesion. TUNEL-positive cells in the RGC layer appeared by 7d post-insult. These results indicate that following induction of
ischemic optic neuropathy, significant axon damage occurs by 3d post-
infarct, with later neuronal death. Post-
stroke adult rat retinal ganglion cells attempt to regenerate their axons, but this effort is restricted to the unmyelinated region of the anterior ON. These responses are important in understanding pathologic process that underlies human non-arteritic
anterior ischemic optic neuropathy (
NAION) and may guide both the appropriate treatment of
NAION and the window of opportunity for such treatment.