Severity of controlled cortical impact traumatic brain injury in rats and mice dictates degree of behavioral deficits

The clinical presentation of traumatic brain injury (TBI) involves either mild, moderate, or severe injury to the head resulting in long-term and even permanent disability. The recapitulation of this clinical scenario in animal models should allow examination of the pathophysiology of the trauma and its treatment. To date, only a few studies have demonstrated TBI animal models encompassing the three levels of trauma severity. Thus, in the present study we characterized in mice and rats both brain histopathologic and behavioral alterations across a range of injury magnitudes arising from mild, moderate, and severe TBI produced by controlled cortical impact injury technique. Here, we replicated the previously observed TBI severity-dependent brain damage as revealed by 2,3,5-triphenyltetrazolium chloride staining (severe > moderate > mild) in rats, but also extended this pattern of histopathologic changes in mice. Moreover, we showed severity-dependent abnormalities in locomotor and cognitive behaviors in TBI-exposed rats and mice. Taken together, these results support the use of rodent models of TBI as a sensitive platform for investigations of the injury-induced neurostructural and behavioral deficits, which should serve as key outcome parameters for testing experimental therapeutics.