Exposure to Acute Psychological Trauma Prior to Blast Neurotrauma Results in Alternative Behavioral Outcomes.

Stress is a common occurrence for military personnel. This can include the stress of deployment and active combat. Anxiety is considered a reaction to stress, and with anxiety-related disorders on the rise, it is imperative that stress be considered a preexisting condition when studying a number of neurological conditions. To determine the effects of stress on the behavioral outcomes of traumatic brain injury (TBI), we used a 3 d acute unpredictable stress (AUS) model followed by blast-induced neurotrauma (BINT) to assess social anhedonia and anxiety-like behaviors in male and female rats. The animals were divided into four groups including unstressed and uninjured control (Con), stress-only animals (AUS), injury-only animals (BINT), and animals that received both stress and injury (AUS + BINT). In the males, behavioral tests such as elevated plus and three-chamber sociability (3-CS) showed that stress plays a dominant role in determining behavioral outcomes after TBI with the AUS + BINT animals behaving more similarly to the AUS animals than the BINT animals. Other tests, such as open field, showed that AUS + BINT had an additive effect on anxiety-like behavior or that prestress could even have a protective effect as seen in three-chamber social novelty (3-CSN). Behavioral assessment of female animals showed that AUS + BINT had the opposite effect than it did on the males in both three-chamber sociability and three-chamber social novelty, while the open field results were similar to the males. This study shows that neurological changes driven by stress have an effect on the behavioral outcomes of BINT.