Context-dependent sensitization to ethanol in zebrafish (Danio rerio)

One of the most robust and readily measurable effects of moderate doses of ethanol on zebrafish behavior is locomotor hyperactivity. Two experiments were designed to examine the effects of repeated exposures to ethanol on ethanol-induced locomotor hyperactivity, and to determine whether these effects are context-dependent. Adult, wild-type zebrafish were given repeated exposure to ethanol in the presence of one contextual stimulus (A), while exposed to water in the presence of a second contextual stimulus (B). Exposure to ethanol consistently induced locomotor hyperactivity. After repeated exposures, animals tested with ethanol in the ethanol-paired context (A) showed sensitization of locomotor activity. When tested with ethanol in the unpaired context (B), however, sensitization was not observed. When tested in the absence of ethanol, there were no differences in responding to the paired and unpaired stimuli. This is the first demonstration of ethanol-induced locomotor sensitization in zebrafish. Moreover, this sensitization was context-specific, indicating that learning can modify drug-induced behaviors in zebrafish.