Short-term and persistent impacts of sublethal exposure to diazepam on behavioral traits and brain GABA levels in juvenile zebrafish (Danio rerio)
2020
Wu, Min | Qiu, Xuchun | Chen, Chen | Chen, Kun | Li, Ming | Xu, Hai | Wu, Xiangyang | Shimasaki, Yohei | Ōshima, Yūji
Environmental pollution by the psychoactive drug diazepam (DZP) has been suggested to disrupt various behavioral traits of fishes. Exposure to DZP in natural waters may be of episodic duration, but there are few reports on the persistence of abnormal behaviors of fishes caused by such acute exposure. In the current study, we exposed juvenile zebrafish (Danio rerio) to sublethal doses of DZP (1200, 120, and 12 μg/L) for four days and evaluated their behavioral traits and brain γ-aminobutyric acid (GABA) levels at days 0 (i.e., immediately after the 4-day exposure), 7, and 21 of the recovery period. Exposure to DZP induced short-term impairment of swimming ability and two-fish interactions of zebrafish. In contrast, DZP induced persistent and/or delayed effects on locomotor activity of zebrafish, i.e., hypoactivity at 1200 μg/L and hyperactivity at 120 and 12 μg/L, that could be still observed on days 7 and/or 21 during the recovery period. DZP exposure also exhibited concentration-specific effects on brain GABA levels in zebrafish, i.e., decreased at 1200 μg/L and increased at 120 and 12 μg/L. Correlation analysis suggested that the changes in brain GABA levels may contribute to the persistence of abnormalities in the locomotor activity of zebrafish. Our findings suggest that zebrafish need a long time to recover from acute exposure to DZP, thus highlighting that the persistence of behavioral abnormalities induced by such psychoactive drugs should be considered in order to better assess their risks in natural ecosystems.
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