Background and aim: Depression is a mental disorder that, according to statistics, is becoming more serious each day, indicating an increasing need for research on depression models and the development of antidepressant drugs. The aim of this study was to evaluate the individual and combined effects of diazepam and escitalopram on behavioral and biochemical parameters in zebrafish (Danio rerio). 

Methods: In this study, Depression was induced in zebrafish using the Unpredictable Chronic Stress (UCS) protocol. A total of 384 zebrafish were divided into two main groups: control (without stressors) and UCS (with stressors). Within each main group, the fish were further divided into four subgroups: control, diazepam, escitalopram, and diazepam + escitalopram, with three replicates per subgroup. Behavioral assessments were conducted using the novel tank test, and biochemical analyses were performed by measuring whole-body cortisol levels. 

Results: Diazepam, escitalopram, and their combination significantly improved behavioral parameters (significant increase in the time spent at the top level and the number of transitions to the top level) and also prevented depressive effects by significantly reducing cortisol levels (from 1.0.1 ± 0.07 to 0.61 ± 0.12 ng of cortisol per gram of tissue). 

Conclusion: This study confirms previous findings indicating that the UCS protocol induces behavioral and neuroendocrine changes in zebrafish, which can be prevented by diazepam and escitalopram administration. Furthermore, the findings support the use of zebrafish as a model organism for studying the behavioral and physiological effects of stress.