The present study investigated the neurobehavioral effects of embryonic exposure to methylmercury (MeHg) in zebrafish using avoidance conditioning as the behavioral paradigm. In this study, adult zebrafish developmentally exposed as embryos to 0.00, 0.01, 0.03, 0.1, or 0.3 µM of MeHg were trained and tested for avoidance responses. The results showed that control zebrafish hatched from embryos unexposed to MeHg learned avoidance responses during training and showed significantly increased avoidance responses during testing. Zebrafish developmentally exposed to MeHg as embryos were hyperactive as they frequently swam back and forth, and showed no significant changes in avoidance responses from training to testing. Results of the present study suggested that embryonic methylmercury exposure produced hyperactivity and impaired avoidance learning.
Key words: Active avoidance conditioning, methylmercury, zebrafish, fish shuttle-box.
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