Sex differences in anxiety‐like behaviors following chronic intermittent ethanol and/or repeated stress exposures using an adult zebrafish (Danio rerio) model

Abstract

Studies on ethanol use have found that stress often impacts responses, such that it may promote increased ethanol intake and, therefore, risk for harm. Additional evidence suggests that stress, especially severe stress, may have a greater negative effect from ethanol in females than males. To improve our understanding of these potential interactions, we used an adult zebrafish model to assess behavioral activities in 6 mth old male and female zebrafish following treatment with chronic intermittent ethanol exposure and/or repeated stress exposure. The 4 treatment conditions were: control (tanks moved to the testing bench but no other manipulations), twice‐daily 60 min 0.5% ethanol exposure and/or 3 times daily 40 sec stress exposures for a total of five days. We used a custom light/dark tank to assess behaviors at approximately 16 hr after the final treatments. Zebrafish were tested individually with data collected for a total of 8 min every 10 seconds: (1) light vs. dark preference, (2) crossings between light and dark, (3) preference for tank top vs. bottom and (4) general activity levels (normal, hyperactive or freezing). Time spent in each activity was summated across the testing period for each animal and averaged by sex within treatment condition. Overall, control females spent more time in the dark (20%) compared to males, suggesting a greater sensitivity to the novelty of the testing tank for female than male fish. We observed a large increase in time spent in the dark for both males (34%) and females (59%) compared to control values for the EtOH‐only treatment whereas the stress + EtOH condition values were similar to controls. There was a prominent sex difference in hyperactivity with the stress only males showing a 26% reduction compared to control levels and females having a 38% increase compared to males. Interestingly, we also saw a reduction (17%) in hyperactivity for EtOH only males compared to control values but a large increase (40%) for the ethanol only females. Again, the stress + EtOH condition values were similar to controls for both sexes, suggestive of some resiliency when exposed to both the intermittent EtOH as well as the repeated stress procedure. We also noted less freezing (believed to reflect high levels of fear/anxiety in the fish) in males and females that were treated with the repeated stress, suggesting that this helped the fish adapt to the novelty of the testing tank more than for the other treatment conditions. These data support the utility of zebrafish as an animal model to study the impact of stress on ethanol responses and showed that behavioral responses support an interaction of stress with ethanol by sex.Support or Funding InformationSupported by Pacific University School of Pharmacy RIG (LLD)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.