Drinks Like a Fish: The Effects of Ethanol on Associative Learning in Zebrafish (Danio rerio)

Abstract

The present study sought to elucidate whether neural maturation has a mitigating effect on ethanol and its concomitant effects on memory. Three-month old zebrafish were acclimated to a plus maze using a habituation procedure. After acclimatization to the maze, associations between the red cue cards and reward were formed via a shaping procedure. Following the final shaping day, food was removed from the maze and red cues were only present in one arm. The time it took for the fish to go from the start box to the cued arm was then measured. Afterwards, fish were exposed to 0.00, 0.25, or 0.75% ethanol (v/v) for 72 hours. Post-exposure memory performance was tested at 0.5-day, 5-day, and 14-day endpoints. Three primary findings were noted. First, no significant difference in run time was found within the control group at any time point, suggesting an adept associative memory system in zebrafish. Second, no significant difference in run time was found when comparing 0.25 and 0.75% (v/v) ethanol groups. Therefore, these treatments were pooled for further analyses. Third, the most significant impairment was observed at the 0.5-day post exposure time point indicating that ethanol has a significant impact on recently learned associations. Finally, no significant difference in run time was observed within the pooled treatment group on subsequent time points. This capacity for recovery was a key difference from what was observed in previous studies.