Zebrafish Are Able to Detect Ethanol in Their Environment.

Abstract

Zebrafish have become a popular animal model for studying the development of alcohol addiction. Several behavioral paradigms for studying alcohol addiction have been developed for zebrafish, including conditioned place preference, alcohol-induced tolerance, and withdrawal. However, alcohol choice preference tasks have not been established in zebrafish as of yet. The ability of zebrafish to detect alcohol in their environment is required in alcohol choice or preference tasks. To our knowledge, it is currently unknown whether zebrafish are able to detect alcohol in their environment immediately following bath immersion. In the current study, we analyzed the time course of alcohol-induced behavioral changes of zebrafish while being immersed in alcohol solution in a 1.5 L tank. We recorded each trial in high-definition and quantified behavioral responses using automated video tracking-based and manual observation-based methods to quantify temporal changes in alcohol-induced behaviors. As alcohol is known to require several minutes of bath immersion to reach the brain in zebrafish, we argued that behavioral responses before this time point would prove zebrafish's ability to detect this substance in the water. Our results show that a 60-min exposure to 1% alcohol alters behavioral responses in a time-dependent manner. Notably, alcohol exposure significantly increased absolute turn angle, decreased distance to bottom, and variance of distance to bottom within the first 3 min immediately following exposure, a response that occurred before alcohol could reach the brain of the subjects in measurable amounts. These results imply that zebrafish are able to detect alcohol in their environment immediately following immersion into the drug solution.