Examining Anxiety and Risk-taking in Healthy Male and Female Wistar Rats using Spatial and Temporal Analysis of Elevated Plus Maze

The Elevated Plus Maze (EPM) offers a standard set up for understanding anxiety, unconditioned risk-avoidance in rodents. The animal shows a preference for enclosed safe arms and avoids risky, open arms that evoke anxiety due to elevated platform (unconditioned response to elevation). A few rodent studies aiming to understand sex-skewed representation in anxiety disorders use the maze and report that more females compared to males show high levels of anxiety and risk-avoidance on an elevated platform. Ethograms derived from examining animal behaviour in the EPM provide precise measures of behaviour of interest, enabling objective assessment of anxiety and risk behaviour. We report two new parameters that might be critical for quantitative analysis of EPM task as a measure of anxiety with reference to sex-differences in risk-taking: (a) spatial preference for arms (open & closed) (b) temporal shift in arm preference in task trials. We first report results from the conventionally derived measures confirming that males spent more time in the open arms indicating low anxiety and higher risk-taking. Preferences for the two open and two closed arms were non-uniform for males and females; male showed stronger preference for one of the two risky open arms, and females showed a stronger preference for one of the two safe closed arms. Temporal analyses indicated that males spent more time in open arms in 3 out of 6 time bins (time blocks), and females spent more time in the closed arms in 5 out of 6 time bins (time blocks), however, counter-intuitively, females showed larger increase in time spent in open arms in the last phase potentially indicating greater regulation of anxiety and increased risk-taking. Inclusion of spatial and temporal parameters in EPM studies might improve our understanding of cognitive and biological sex-differences pertaining to anxiety, and risky behaviour.