Introduction: Experimental traumatic brain injury (TBI) elicits acute local inflammatory responses, including up-regulation of adhesion molecules and neutrophils in the injured brain. However, in clinical experiences there were at least three types of TBI, which included mild, moderate and severe types, and there would be different neuroinflammatory responses. This study investigated the inflammatory responses after mild TBI in rats.
Methods: Adult male Sprague-Dawley rats (n = 40) were group-housed and injured using an impact method. Motor function was assessed 1-4 days after the injury by using a grip test (Grip strength meter; Singa). Blood samples collected from the rats before the injury and after the injury and the Intercellular adhesion molecule-1 (ICAM-1) level were measured.
Results: The ICAM-1 expression from pre-injury to post-injury showed a significantly greater gradual elevation in the rats in the mild-injury group than in the moderate-injury group. The neurological function evaluated with grip test showed no deterioration of neurological function in the mild-injury group but gradual deterioration in the moderate-injury group.
Conclusion: These findings showed a delayed inflammatory reaction in the mild-injury group without progressive deterioration of neurological function. Therefore, in the moderate-injury group, no progression phase was observed.