Acute effects of alcohol and nicotine on behaviour in proactive and reactive zebrafish coping styles

Alcohol and nicotine are psychoactive substances that contribute to significant health risks and serious medical problems. Although the biological consequences of alcohol and nicotine have been studied extensively, the individual variation in the behavioural effect of these drugs has not been fully elucidated yet.

In this study, we hypothesise that exposure to alcohol and nicotine results in distinct behavioural changes that vary between individuals with proactive or reactive coping styles. To test this hypothesis, we analysed the locomotor activity of proactive, reactive and non-selected zebrafish larvae, treated with acute concentrations of alcohol (0.5%, 1%, 2%), nicotine (5 μg L^-1, 25 μg L^-1, 50 μg L^-1) and a combination of both drugs (0.5% + 5 μg L^-1; 0.5% + 25 μg L^-1; 0.5% + 50 μg L^-1). We performed a light-dark challenge behavioural assay, wherein alternating dark and light phases elicited an anxiety-like response.

Our findings reveal a concentration-, drug type- and coping style-dependent response. For animals treated with alcohol, individuals with a proactive coping style were more affected by the biphasic effect of this drug, which induced greater locomotor activity during the habituation phase as compared to reactive and non-selected animals. Conversely, nicotine exposure reduced activity in response to dark conditions similarly in pro- and reactive coping styles. In addition, proactive and reactive fish exhibit concentration-dependent responses distinct from non-selected animals during the light phase.

These findings highlight the importance of considering different behavioural coping styles when studying the effects of psychotropic substances, potentially contributing to a better understanding of the underlying mechanisms of variation in responses to drugs of abuse.