Impacts of chronic exposure to sublethal diazepam on behavioral traits of female and male zebrafish (Danio rerio)

Residues of the psychoactive drug diazepam (DZP) may pose potential risks to fish in aquatic environments, especially by disrupting their behavioral traits. In this study, female and male zebrafish were subjected to chronic exposure (21 days) to sublethal doses (120 and 12 mu g/L) of DZP, aimed to compare the characteristics of their behavioral responses to DZP exposure, and to investigate the possible links between those behavioral responses and variations in their brain gamma-aminobutyric acid (GABA) and acetylcholinesterase (AChE) levels. Chronic exposure to DZP significantly decreased the swimming velocity and locomotor activity of both genders, indicating a typical sedative effect. Compared with males, whose locomotor activity was only significantly decreased by exposure to DZP for 21 days, females became hypoactive on day 14 (i.e., more sensitive), and they developed tolerance to the hypoactive effect induced by 120 mu g/L DZP by day 21. Exposure to DZP significantly disturbed the behavioral traits related to social interactions in females but not in males. Those results indicate that DZP exhibits sex-dependent effects on the behaviors of fish. Moreover, exposure to DZP for 21 days significantly disturbed almost all of the tested behavioral traits associated with courtship when both genders were put together. Sex-dependent responses in brain GABA and AChE levels due to DZP exposure were also identified. Significant relationships between the brain GABA/AChE levels and some behavioral parameters related to locomotor activity were detected in females, but not in males.

Automated summary

The study found that chronic exposure to diazepam (DZP) led to decreased swimming velocity and locomotor activity in both female and male zebrafish, with females being more sensitive and developing tolerance to the hypoactive effect induced by DZP. DZP also exhibited sex-dependent effects on social interactions and courtship behaviors in fish, as well as on brain gamma-aminobutyric acid (GABA) and acetylcholinesterase (AChE) levels.