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G. Parrilla–Reverter, II, P. Sobrado–Calvo, I. Cánovas, J.M. Bernal, M.I. Soro, M.E. Aguilera, M.P. Villegas–Pérez, M. Vidal–Sanz; Retinal Ganglion Cell Axotomy Induced by Intraorbital Nerve Crush or Optic Nerve Transection Results in Different Time Course Degeneration and Expression of Neurofilaments . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1248.
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To investigate the time course of the retinal ganglion cell (RGC) and nerve fiber layer (NFL) degeneration induced by intraorbital optic nerve crush (IONC) or intraorbital optic nerve transection (IONT).
Adult Sprague–Dawley rats were anaesthetized and the left optic nerve (ON) was exposed within the orbit. Under microscopic control the left ON was crushed with fine angulated jeweller's forceps, approximately 3 mms from the optic disc, or was completely transected close to its origin, at approximategly 0.5 mms from the optic disc. Care was taken not to damage blood supply to the retina. Degeneration in retinal ganglion cells and the nerve fiber layer was examined with RT97 antibodies recognizing the phosphorilated heaviest subunit of the neurofilament triplet, at various survival intervals ranging 1 week to 3 months after axotomy.
Uninjured retinas showed typical RT97 staining of the RGC axons within their most concentric aspects in the retina, resulting in an intense labelling of the central region of the nerve fiber layer. There were no RGCs labelled for RT97. As early as 7 days after IONC many degenerating features appeared throughout the RGC and RFL. These included; i) an RT97 staining of the axons from the central to the periphery; ii) the presence of RGCs very intensely labeled with RT97 that appeared as bulbs; iii) Axonal degeneration features consisting in intense RT97 labelling of beadings spread throughout their entire intraretinal course, and; iv) few RGCs located on the mid–periphery that were intensely positive for RT97 immunoreactiviy. These features increased in frequency with longer survival intervals after axotomy and peaked between day 14 and 21 after IONT. By 30 days, the number of degenerating features had drastically reduced, and the number of RT97 immunopositive axons in the center of the retina had reduced drastically to a small fraction of the original population. Retinas that underwent IONT showed qualitatively the same features, however these appeared more slowly resulting in greater numbers of RT97 axons in the central retina for the same survival periods of time. At longer time intervals, such as 1, 2 or 3 months, there were fewer RT97 stained fibers in the IONT group than in the IONC group.
Following axotomy of the RGC population there is a progressive degeneration of RGCs and their axons that appear earlier and more intense after IONT than after IONC.
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