Abstract
Purpose: :
To investigate long term light-induced retinal degeneration in the albino rat and to compare it with light-induced retinal degeneration in the pigmented rat (Marco-Gomariz et al, J Comp Neurol 498(2006):163-179) and inherited retinal degeneration in the dystrophic RCS-p+ rat (Villegas-Pérez et al., J. Comp. Neurol. 392 (1998): 58-77; Wang et al., Curr. Eye Res. 27(2003): 183-196).
Methods: :
Sprague-Dawley rats were exposed to light (3000 lux) for 48 hours. The left pupil was previously dilated with topical atropine. Before processing, the eye fundus was inspected, Horseradish Peroxidase (HRP) was injected intravenously or Fluoro-gold (FG) was applied to the superior colliculli to retrogradely label Retinal Ganglion cells (RGCs). Animals were processed between 0 and 9 months after light exposure (ALE) and the retinas dissected as whole mounts or cross-sectioned and reacted for HRP demonstration or incubated with antibodies. The retinas were examined and photographed and reconstructions of the whole mounts were made using Image-Pro Plus 5.0 for Windows®. FG-labelled RGCs were counted in each retina using the same software (Salinas-Navarro et al., Vision Res. 49(2009): 115-126).
Results: :
Albino rats showed in the first week ALE an arciform area of heightened light sensitivity in the superotemporal retina that exhibited HRP leakage. Photoreceptor loss later spread throughout the retina. Three months ALE the outer nuclear layer had almost completely disappeared, while the other retinal layers showed a reduction in thickness. Photoreceptor degeneration proceeded at a faster pace in the left dilated eyes than in the right non-dilated eyes, but only during the first month ALE. Both retinas of the animals processed 6 months or more ALE showed thinning of the main retinal vessels and compression of the nerve fiber layer axons by the innermost retinal vessels. The numbers of RGCs decreased in both eyes significantly six or more months ALE.
Conclusions: :
Light-induced retinal degeneration affects with time all the retinal layers and proceeds faster in albino than in pigmented rats, but at a similar rate to the degeneration found in dystrophic RCS rats. Both inherited and light-induced retinal degeneration affect with time all retinal layers causing vascular and axonal alterations that are therefore secondary to photoreceptor degeneration and not inherent to the disease.
Keywords: retinal degenerations: cell biology • radiation damage: light/UV • inner retina dysfunction: biochemistry and cell biology