[Changes in number and distribution of retinal ganglion cells after optic nerve crush in zebrafish]

Changes in number and distribution of retinal ganglion cells were studied after optic nerve crush in zebrafish (Brachydanio rerio) with retinal wholemount. There were approximately 40,000 to 56,000 cells in the retinal ganglion cell layer. The density of ganglion cells was divided into six classes and the area of highest cell density (central area) was located at the temporal area to the optic disc in normal fish. At the early regeneration stages after optic nerve crush, the percentage of lost cells increased gradually. Cell density had fallen first in the central area. At the late regeneration stages, there was an approximately 20% loss of ganglion cells during optic nerve regeneration. The results suggest that the loss of cells may undergo apoptosis rather than necrosis. A wave of cell loss started in the central area and spread progressively further into periphery. The reason caused these changes may be due to temporal interruption of optic nerve function, recovery from crush and the ability to quickly regenerate in optic nerve of the fish.