Repeated mild traumatic brain injury produces neuroinflammation, anxiety-like behaviour and impaired spatial memory in mice

Primary Objective: Repeated traumatic brain injuries (rmTBI) are frequently associated with debilitating neuropsychiatric conditions such as cognitive impairment, mood disorders, and post-traumatic stress disorder. We tested the hypothesis that repeated mild traumatic brain injury impairs spatial memory and enhances anxiety-like behaviour. Research Design: We used a between groups design using single (smTBI) or repeated (rmTBI) controlled cranial closed skull impacts to mice, compared to a control group. Methods and Procedures: We assessed the effects of smTBI and rmTBI using measures of motor performance (Rotarod Test [RT]), anxiety-like behaviour (Elevated Plus Maze [EPM] and Open Field [OF] tests), and spatial memory (Morris Water Maze [MWM]) within 12 days of the final injury. In separate groups of mice, astrocytosis and microglial activation were assessed 24 hours after the final injury using GFAP and IBA-1 immunohistochemistry. Main Outcomes and Results: RmTBI impaired spatial memory in the MWM and increased anxiety-like behaviour in the EPM and OFT. In addition, rmTBI elevated GFAP and IBA-1 immunohistochemistry throughout the mouse brain. RmTBI produced astrocytosis and microglial activation, and elicited impaired spatial memory and anxiety-like behaviour. Conclusions: rmTBI produces acute cognitive and anxiety-like disturbances associated with inflammatory changes in brain regions involved in spatial memory and anxiety.