Stress and risk avoidance by exploring rats: implications for stress management in fear-related behaviours

Animals display protective patterns of behaviour. Adoption of such protective patterns requires the assessment of risks posed by the environment and subsequent avoidance of high-risk locations. We hypothesized that adverse experiences lead to formation of a context-specific memory, thus changing the pattern of exploratory behaviours in response to specific cues associated with this experience. Here we examined exploratory movement patterns and compared approach/avoidance behaviours in rats following a stressful experience in the same versus a different environment. Using an open table exploration task, we compared exploratory movements in rats that were either stressed by restraint in a different environment or stressed in the test environment. The following day rats were allowed to explore the open table environment. Different test situations were provided in which rats were given access to a refuge or a large visual object as placed in the vicinity to the open table. The results indicate that stressed rats avoid the specific location associated with a stressful experience. However, when provided with a refuge in this location the salience of the stressful memory is reduced and the refuge will become a preferred location. Exploratory patterns and avoidance behaviours were correlated with corticosterone levels. Behavioural changes were not related to dendritic morphology in the medial prefrontal cortex (layer III). The results provide insights into risk avoidance strategies in rats and suggest that environmental intervention can reverse stress-related changes in behaviour.