Changes in goldfish retinal ganglion cells during axonal regeneration

Recent work suggests that mammalian retinal ganglion cells may become more like developing ganglion cells in form while regenerating through a peripheral nerve graft. We have injected Lucifer Yellow into regenerating ganglion cells of goldfish to look for similar changes. Within three weeks of injury, we saw dye-coupling to nearby cells, which is a common developmental feature in many species. Dendrites and axons, which in most mature ganglion cells are smooth, became varicose and hairy, like those examined in mammalian development. Secondary axons arose later, not only as side-branches of the primary axon but also from the soma, as in mammalian development and regeneration. Since, in fish, these responses are clearly an intrinsic part of functional regeneration, their equivalence in fish and mammals strengthens the view that a similar regenerative competence may exist in the retinal ganglion cells of all vertebrates.