Effects of Environmental Enrichment in a Mouse Model of Posttraumatic Stress Disorder

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Posttraumatic stress disorder (PTSD) may appear after an individual experiences a stressful situation. It is characterized by the avoidance of situations that are related to the trauma and persistent hyperarousal, which may become associated with anxiety and cognitive disability. The present study evaluated the effects of environmental enrichment on anxietylike behavior and memory in a mouse model of PTSD that employed different reexposures to situational reminders (SRs; 1 or 10 min). Male Swiss mice were exposed or not exposed to environmental enrichment and then subjected to the model of PTSD in a light-dark box. After exposure to the aversive stimulation, the animals were evaluated in a light-dark box, a modified light-dark box, the elevated plus maze (EPM), and the novel object recognition test. Environmental enrichment attenuated the effects of footshock, did not alter anxietylike behavior or memory in animals that were exposed to 1-min SRs, increased anxietylike behavior and memory in animals that were exposed to 10-min SRs, and reversed behavioral sensitization in the EPM. The results suggest that environmental enrichment does not mitigate the effects of reexposure to 1-min SRs on traumatic memory and favors the maintenance of traumatic memories, even when animals are reexposed to SRs for 10 min. However, environmental enrichment reversed the effects of the aversive stimulation on behavioral sensitization. The effects of environmental enrichment in the present model of PTSD are complex and depend on the duration of SRs and the specific behaviors that are assessed.

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