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J.I. Matsui, A.L. Egana, T.R. Sponholtz, A.R. Adolph, J.E. Dowling; Effects of ethanol on the development of photoreceptors in embryonic zebrafish . Invest. Ophthalmol. Vis. Sci. 2004;45(13):5301.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Some children who are born to mothers who have consumed alcohol during pregnancy present a number of morphological, cognitive, and sensory abnormalities, including vision deficits, collectively known as fetal alcohol syndrome (FAS). The retina is one of the organs affected in children with FAS. The goal of this study is to determine if the zebrafish retina is a good model system to study retinal and visual function abnormalities caused by exposure to ethanol during embryogenesis. Methods: Photoreceptor differentiation commences at 2 days post–fertilization (dpf) and by 5 dpf, the differentiation of the photoreceptor layer is easily observable by light microscopy. Zebrafish embryos were raised in fish water supplemented with varying concentrations of ethanol (1.5%–2% per volume) from 2 dpf through 5 dpf. Photoreceptor morphology was examined using light– and transmission electron microscopy. Visual thresholds from treated and untreated animals were measured using an optokinetic response (OKR) behavioral assay. To assess retinal function, full–field electroretinograms (ERGs) were performed under photopic conditions. Results: Ethanol treatment resulted in a significant reduction in the size of the retina. Furthermore, electron microscopy showed morphological changes in the photoreceptor outer segments. Ethanol–treated animals also exhibited a consistent increase in visual threshold as determined by OKR behavioral testing and they showed a significant decrease in the amplitude of both the b– and d–wave of the ERG. Conclusions: Ethanol treatment of zebrafish embryos during the period of photoreceptor differentiation results in decreased eye size and inhibition of outer segment differentiation, which could explain the deficits in visual function. These results mirror those obtained by investigators who have analyzed the effect of ethanol in visual function in mammalian systems. Zebrafish may prove to be a useful model system to study the molecular mechanisms underlying the development of FAS.
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