Evidence that regenerating optic axons maintain long-term growth in the lizard Ctenophorus ornatus: growth-associated protein-43 and gefiltin expression.

In the lizard, Ctenophorus ornatus, the optic nerve regenerates but animals remain blind via the experimental eye, presumably as a result of axons failing to consolidate a retinotopic map in the optic tectum. Here we have examined immunohistochemically the expression of the growth-associated protein GAP-43 and the low-molecular-weight intermediate filament protein gefiltin, up to one year after optic nerve crush. Both proteins were found to be permanently up-regulated, suggesting that regenerating axons are held in a permanent state of re-growth. We speculate that, in the lizard, the continued expression of GAP-43 and the failure to switch from the expression of low- to high-molecular-weight intermediate filament proteins are associated with the inability to consolidate a retinotopic projection.