Inescapable exposure to the Barnes maze increases preference for alcohol over water in rats: Implications for depression and anxiety

Abstract

Various sources of stress induce alcohol intake in rodents, including inescapable shocks, physical restraint, and reward loss. One hypothesis maintains that alcohol intake increases because its anxiolytic properties reduce negative emotion. A series of experiments explored this hypothesis using escapable vs. inescapable exposure to the well-lit circular platform of a Barnes maze in a master/yoked (M/Y) design, with pairs of rats matched in the amount of time on the lighted platform, but differing in terms of the presence vs. absence of an escape box. In Experiment 1 the M/Y design was validated as a means of producing rapid acquisition of escape behavior in master animals. In Experiment 2, immediate postsession access to a 2-h, 2-bottle preference test with 8 % alcohol and water resulted in a higher increase in preference for alcohol over water across sessions in yoked animals compared to master animals. Group differences were not observed when animals had access to water in both bottles. Higher preference for 8 % alcohol in yoked vs. master animals was also observed when the Barnes maze and preference test were separated by a 1-h interval (Experiment 3). However, voluntary alcohol consumption was similar in master and yoked animals when the order of exposure to the Barnes maze and fluid consumption was reversed (Experiment 4) or when the threat level was reduced by using a dim light over the Barnes maze (Experiment 5). Increased preference for alcohol after inescapable exposure to the Barnes maze is consistent with the hypothesis that alcohol alleviates negative mood and anxiety induced by an inescapable threat. This animal model is relevant to an understanding of the initial stages of co-morbidity between depression, anxiety, and alcohol use.