A comparative study on the acute-phase behavioral and pathological responses of closed head injury induced by cranial vertex and temporal lobe impacts in male rats

The outcomes of traumatic brain injury (TBI) are closely linked to the strength of mechanical loads applied to the head. However, the same mechanical load can lead to significant variations in injury outcomes depending on the location of impact. To compare the acute-phase behavioral and pathological effects of different impact locations on TBI outcomes, we conducted a closed head injury experimental study using male rats subjected to cranial vertex and temporal lobe impacts. The rats were injured by an impactor according to the experimental protocol established using the L₄ (2³) orthogonal table, and the behavioral and pathological outcomes were assessed. The contribution rates of impact location and strength to TBI were quantified using Analysis of Variance. The results indicated that impact strength played a dominant role in TBI and showed a positive correlation, while the role of impact location in TBI cannot be ignored. Behaviorally, cranial vertex impacts led to more severe coma, motor, memory, and anxiety deficits. Pathologically, cranial vertex impacts caused more severe diffuse axonal injury in the corpus callosum and brainstem. In the left hippocampus and amygdala, cell loss due to cranial vertex impacts was more pronounced than that caused by temporal lobe impacts, whereas the opposite was true on the right side. Notably, the pathological changes observed in the left (non-impact) hippocampus and amygdala due to temporal lobe impacts showed a stronger linear correlation with behavioral outcomes, suggesting that damage to the left side has greater predictive power for behavioral deficits. This suggests that the impact location is an important factor affecting TBI and should be considered in the study.