Behavioural and molecular effects of alcohol in the stress model of zebrafish

Abstract

Objectives: Stress and anxiety disorders are common health problems that have been related to an increase in the likelihood of developing addictions, which have individual and social consequences. Although socially acceptable, alcohol is a substance that can generate dependence and abuse. Alcohol misuse, its relationship with stress and its consequences have been studied; however, multiple limitations are placed on clinical research in humans. In this exploratory work, we analysed the behavioural and molecular effects of joint exposure to ethanol and an unpredictable stress protocol (USP) in adult zebrafish. Materials and Methods: Adult zebrafish behaviour was studied employing unpredictable stress and behavioural tests. The tests were performed in stressed and nonstressed animals with and without exposure to known concentrations of alcohol. To evaluate the behaviour, tracking techniques were used on video recordings and parameters such as distance travelled, swimming speed and place preference as well as aggression patterns with mirror proximity tests were measured. In the control and 0.75% alcohol group, the expression of candidate stress-related genes (slc6a4a, slc6a3, comta and bdnf3) was analysed by RT-qPCR. Results: The results showed that concentrations of 0.75% alcohol reduced the locomotor activity of the fish, which can be interpreted as an increase in the anxiolytic effect of alcohol under nonstress conditions. Expression of comta, bdnf3 and slc6a3 was reduced in the stress and stress plus 0.75% ethanol groups and expression of slc6a4a was increased in the stress plus 0.75% alcohol group. Conclusion: Our exploratory work contributes novel insights about the molecular and behavioural effects of the combination of unpredicted stress and alcohol misuse. The USP and ethanol exposure increase anxiety behaviour and reduce the expression of genes involved in brain homeostasis. Future study of other pharmacological compounds and additional genes will be helpful for a deeper understanding of the molecular mechanisms involved in the response to stress and alcohol use.