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Evaluating alterations in Zebrafish retino-tectal projections as an indication of developmental neurotoxicity
Citation:
COWDEN, J., C. Y. Fan, D. Hunter, B. Padnos, K. Jensen, T. V. RAMABHADRAN, AND S. J. PADILLA. Evaluating alterations in Zebrafish retino-tectal projections as an indication of developmental neurotoxicity. Presented at Society of Toxicology Annual meeting, Salt Lake City, UT, March 07 - 11, 2010.
Impact/Purpose:
To determine ifaltered retino-tectal projection area-is-an endpoint indicative of developmental neurotoxicity, zebrafish embryos were exposed to four chemicals (retinoic acid, cadmium, valproate, and ethanol) with evidence of developmental neurotoxicity in mammalian systems, and three chemicals (saccharin, amoxicillin, and omeprazole) without such evidence.
Description:
The U.S. EPA is developing alternative screening methods to identify putative developmental neurotoxicants and prioritize chemicals for additional testing. One method developmentally exposes zebrafish embryos and assesses nervous system structure at 2 days post-fertilization (dpf). Previous data indicated that exposure to developmental neurotoxicants reduced retino-tectal projection area. To determine ifaltered retino-tectal projection area-is-an endpoint indicative of developmental neurotoxicity, zebrafish embryos were exposed to four chemicals (retinoic acid, cadmium, valproate, and ethanol) with evidence of developmental neurotoxicity in mammalian systems, and three chemicals (saccharin, amoxicillin, and omeprazole) without such evidence. All experiments were conducted in 96well plates at 26°C. Zebrafish embryos were exposed to a range of chemical sublethal concentrations from 6 hours to 2 dpf. At 2 dpfnervous system structure was examined by whole mount anti-acetylated o-tubulin staining and retino-tectal projection area was measured. All measurements were made blinded for dose. Ofthe chemicals examined, valproate, ethanol, and retinoic acid showed a dose-dependent decrease in retino-tectal projection area. Furthermore, quantitative real-time PCR (qRT-PCR) demonstrated that exposure to valproate or ethanol alters levels of brn3c, a transcription factor important for optic tectum development. These preliminary results suggest that changes in retino-tectal projection area may correlate with developmental neurotoxicity in mammals and such changes might be measured rapidly using qRT-PCR.