[Research on anxiety-like neurobehavior of zebrafish caused by lead exposure and its mechanism]

Objective: This study aims to explore whether lead exposure could cause anxiety of zebrafish larvae, and to explore its mechanism. Methods: In May 2020, zebrafish embryos 4 hours after fertilization (4 hpf) were collected, E3 culture medium was used as the control group, and different lead exposure concentrations (6, 12, 24, 48 μmol/L) as the poisoned group during the time was 140 h. The mortalities, hatching rates and deformity rates were calculated, the behavioral changes of 144 hpf larvae were observed (moving speed, moving distance, activity, absolute turn angle, the light-evoked startle response, darkness-evoked escape response and thigmotaxis) . The levels of reactive oxygen species (ROS) and malondialdehyde (MDA) were detected in zebrafish larvae in the heads. ELISA kits were used to detect the expression of 5-hydroxytryptamine (5-HT) , dopamine (DA) , noradrenaline (NA) and corticotropin-releasing hormone (CRH) related to anxiety. Results: The mortalities rates of zebrafish embryos in the lead exposure concentration of 12, 24 and 48 μmol/L were higher than the control group, and the embryo hatching rates were lower than control group. The deformity rates of zebrafish larvae in the lead exposure concentration of 24 and 48 μmol/L were higher than control group (P<0.01) . The movement speed, activity and thigmotaxis of zebrafish larvae in the lead exposure concentration of 24 and 48 μmol/L were significantly lower than control group, the absolute turn angle were higher than control group (P<0.01) . The moving distance and darkness-evoked escape response of zebrafish larvae in the lead exposure concentration of 48 μmol/L group were lower than control group (P<0.05) . The light-evoked startle response of zebrafish larvae in the lead exposure concentration of 12, 24 and 48 μmol/L groups were lower than control group (P<0.05) . The ROS levels and MDA concentrations in the heads of larvae in the lead exposure concentration of 24 and 48 μmol/L were higher than control group (P<0.05) . The levels of NA and DA in the heads of the larvae in the lead exposure groups of 12, 24 and 48 μmol/L were lower than control group, and the levels of 5-HT and CRH in the heads of the larvae in the lead exposure groups of 24 and 48 μmol/L were higher than control group (P<0.05) . Conclusion: Lead exposure is toxic to zebrafish embryonic development and may cause anxiety-like neurobehavior changes and oxidative stress in zebrafish.