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High-speed optical mapping of heart and brain voltage activities in zebrafish larvae exposed to environmental contaminants
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International audience. Environmental contaminants represent a poorly understood ecotoxicological and healthrisk. Here, we advanced a high-speed optical mapping (OM) technique to non-invasivelytrack voltage dynamics in living zebrafish larvae’s heart and brain and investigate theeffects of selected pesticides.OM allowed high resolution (∼17x) and fast acquisition (100 to 200 frames/s) ofthe voltage signal generated in the heart and brain after immersion of the zebrafishlarvae in a voltage-sensitive dye. First, we used varying temperatures (20 ◦C to 25◦C) to test the adequacy of OM in capturing cardiac and brain voltage changes. Then,we tested the effects of glyphosate or a selected pesticide cocktail (2 to 120 h post-fertilization), accounting for their environmental thresholds and mimicking high-levelexposure. Glyphosate (0.1 and 1000 μg/L) and the pesticide cocktail (0.1 and 10 μg/L)did not alter cardiac activity, except for a trend increase in heart rate variability athigh glyphosate dose. Fourier transform (FT) analyses indicated that glyphosate reducedthe abundance of low-amplitude voltage activities in the brain at the target low-frequency range of 0.2–15 Hz. The anatomical fragmentation of the brain into fourregions, right and left diencephalon (RD and LD) and right and left optic tectum (ROTand LOT), confirmed the impact of glyphosate on the larvae brain and revealed a specificadaptation to the pesticide cocktail in the RD and ROT regions.In summary, OM captured heart and brain voltage changes in zebrafish larvae, withdiscrete patterns of brain depolarization in the presence of specific water contaminants.Here we discuss the relevance of these findings to ecotoxicology and exposome research.
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