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Marguerite Wasowicz, Cécile Morice, Patricia Ferrari, Jacques Callebert, Claudine Versaux-Botteri; Long-Term Effects of Light Damage on the Retina of Albino and Pigmented Rats. Invest. Ophthalmol. Vis. Sci. 2002;43(3):813-820.
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purpose. To observe the morphology and physiology of the retina in rats 11 weeks
after a constant (24-hour) but moderate (500-lux) illumination for 1
methods. Levels of aspartate, γ-aminobutyric acid (GABA), glutamate,
glutamine, and taurine were measured by high-pressure liquid
chromatography (HPLC) in the retina and vitreous humor of albino
(Wistar) and pigmented (Long-Evans) rats. Semithin sections were used
to determine retinal morphology. The TUNEL method was used to detect
cells degenerating by apoptosis. Because the GABAergic system has been
shown to be particularly sensitive to the loss of photoreceptors, an
additional immunohistochemical study using anti-GABA, anti-glutamate
decarboxylase (GAD)67 and anti-GAD65 antibodies
results. No apparent morphologic changes were found in the retina of pigmented
rats after constant illumination, whereas in albino rats disappearance
of photoreceptors (except in the extreme retinal periphery) and cell
bodies was observed. A significant number of TUNEL-positive nuclei also
occurred in the remaining nuclear and ganglion cell layers. However, no
change in the distribution of GABA, GAD67, and
GAD65 immunoreactivities was found in either strain under
constant illumination compared with control animals. Constant
illumination affected the retinal levels of aspartate, glutamate,
glutamine, glycine in both strains, whereas GABA contents did not
change and taurine was decreased only in albino rats. A significant
increase of vitreal glutamate levels was also found in both strains and
of taurine levels only in albino rats.
conclusions. Phototoxicity can provoke durable retinal alterations beyond the period
of lighting, suggesting progressive and probably continuous
modifications of retinal physiology, even in pigmented animals in which
the retina seems morphologically normal.
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