Pharmacological analysis of zebrafish (Danio rerio) scototaxis

The scototaxis test has been introduced recently to assess anxiety-like phenotypes in fish, including zebrafish. Parametric analyses suggest that scototaxis represents an approach-avoidance conflict, which hints at anxiety. In this model, white avoidance represents anxiety-like behavior, while the number of shuttling events represents activity. Acute or chronic fluoxetine, buspirone, benzodiazepines, ethanol, caffeine and dizocilpine were assessed using the light-dark box (scototaxis) test in zebrafish. Acute fluoxetine treatment did not alter white avoidance, but altered locomotion in the higher dose; chronic treatment (2 weeks), on the other hand, produced an anxiolytic effect with no locomotor outcomes. The benzodiazepines produced a hormetic (inverted U-shaped) dose-response profile, with intermediate doses producing anxiolysis and no effect at higher doses; clonazepam, a high-potency benzodiazepine agonist, produced a locomotor impairment at the highest dose. Buspirone produced an anxiolytic profile, without locomotor impairments. Moclobemide did not produce behavioral effects. Ethanol also produced a hormetic profile in white avoidance, with locomotor activation in 0.5% concentration. Caffeine produced an anxiogenic profile, without locomotor effects. These results suggest that the light-dark box is sensitive to anxiolytic and anxiogenic drugs in zebrafish.