Polybrominated diphenyl ethers (PBDEs) cause neurobehavioral toxicity, but their effects on visual behavior remain unknown. In the present study, the impact of PBDEs on visual behavior was examined using optokinetic responses and phototaxis in zebrafish larvae. Zebrafish embryos were exposed to pentabrominated diphenyl ethers mixture (DE-71) at concentrations of 0, 0.32, 3.58, and 31.0 µg/L until 15 d postfertilization. The authors then assessed photoreceptor opsin expression, retinal histology, and visual behavior of the larvae. The results showed that the transcriptions of the opsin genes, zfrho and zfgr1, were significantly upregulated. Western blotting further demonstrated a significant increase in rhodopsin protein expression after exposure of the larvae to DE-71. Histological examination revealed the following morphological alterations in the retina: increased area of inner nuclear layer, decreased area of inner plexiform layer, and decreased density of ganglion cells. Tests of optokinetic and phototactic behavior showed hyperactive responses on exposure to DE-71, including increased saccadic eye movements and phototactic response. The present study is the first to demonstrate that the acute exposure of zebrafish larvae to DE-71 causes biochemical and structural changes in the eye that lead to behavioral alterations. Analysis of these visual behavioral paradigms may be useful in predicting the adverse effects of toxicants on visual function in fish.
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