White Environment Can Be Used as an Aversive Stimulus in Zebrafish Inhibitory Avoidance Learning

The two-factor theory predicts that the acquisition of avoidance responses is dependent on fear reduction; as such, drugs that reduce or increase fear or anxiety states should alter inhibitory avoidance (IA) acquisition. The present experiment used white spaces as aversive unconditioned stimuli in IA in zebrafish. Adult zebrafishes were tested in three experiments: validation of white compartment as aversive in IA; open field test; and effect of antidepressant (fluoxetine, imipramine) and anxiolytic (diazepam, clonazepam). The data show the effectiveness of the white compartment as an aversive stimulus in IA. Antidepressant fluoxetine did not alter and imipramine impairs avoidance acquisition in higher doses. Imipramine also produced a sedative effect in lower doses. Anxiolytic and stimulant drugs facilitated learning at doses which did not impair locomotion, suggesting that pharmacological manipulation of other factors in addition to fear/anxiety can impact aversive learning in zebrafish.