Resumo

Objectives: to assess the predictive validity of anxiolytic drugs on putative behavioral parameters of anxiety in zebrafish (Danio rerio) and to develop fast, simple and valid anxiety tests, we investigated the behavioral responses of zebrafish acutely treated with different anxiolytics on a protocol (the Group Behavior Task) that assesses simultaneously behavioral parameters. The usefulness of the light/dark task a screening method was also evaluated. Methods: zebrafish were treated with different concentrations of benzodiazepines (clonazepam, bromazepam and diazepam), ethanol, buspirone and propranolol in four behavioral parameters (height in the tank, locomotion, color, and shoal cohesion). Drug concentrations were determined based on pilot drug response curves and the relative potency of drugs or chosen based on previous data. Raters were blind to treatment groups and a control group was included in every experiment. In order to observe shoaling of adult zebrafish in a novel task, we developed a protocol called the Group Behavior Task (n=3 per group). This was conducted initially in 50 min sessions and later in a 10 min session. Zebrafish (n=12) were also tested individually for 5 min in the light/dark task (time in the light zone, number of crossings and latency of first crossing). Protocols were approved by the Ethics Committee of PUCRS. Results and conclusion: The benzodiazepines clonazepam (F4,59=13.5, p<0.001), bromazepam (F4,59=25.7, p<0.001) and diazepam (F4,59=29.4, p<0.001) significantly reduced shoal cohesion in Group Behavior Task. Buspirone specifically increased height of zebrafish in the tank (F4,59=22.4, p<0.001) but failed to affect shoal cohesion. Ethanol affected all behavioral parameters whereas Propranolol only reduced locomotion and height. In the light/dark task, all benzodiazepines, buspirone, and ethanol increased time spent in the light compartment. After treatment with anxiolytics, fish typically spent more than 60 s and rarely less than 40 s in the light compartment whereas controls (n=45) spent 33.3 ± 14.4 s and always less than 60 s in the light compartment. These results suggest that light/dark preference in zebrafish is a practical, low-cost, and sensitive screening task for anxiolytic drugs. Height and shoal cohesion are useful behavioral parameters in discriminating different classes of these drugs.