Objective       To investigate the role of TNF-α inhibitor during early brain injury after subarachnoid hemorrhage in rats.      Methods       Forty-eight adult male SD rats were randomly and equally divided into 4 groups

sham-operation group

subarachnoid hemorrhage group

vehicle group and TNF-α inhibitor group. TNF-α inhibitor (monoclonal antibody) or PBS of 10 μl was injected into lateral cerebral ventricle of corresponding rats in 30 min before subarachnoid hemorrhage model establishment. Then the model was induced by injecting autologous arterial blood into the prechiasmatic cistern. After general condition and nerve function were evaluated in 24 h after model establishment

all rats were killed and their brain was resected. Expressions of TNF-α in the cortex were observed by immunohistochemistry

and the protein expression was examined by Western blotting. The clinical assessment was also examined. Brain Evan’s blue contents in rat brains were measured at same time points by formamide extraction method.      Results       Immunohistochemistry showed that the expression of TNF-α was increased dramatically in SAH group

which was higher than that of sham group

but that was decreased significantly in TNF-α inhibitor group. Western blotting showed MMP-9 expression was lower in sham group

and higher in SAH group in the cortex (P0.01). Compared to SAH group

the expression of MMP-9 was decreased significantly in TNF-α inhibitor group (P0.01). The clinical assessment showed that the clinical behavior of rats was improved significantly in TNF-α inhibitor group (P0.01).      Conclusion      TNF-α inhibitor improves the clinical assessment of SAH rats and protects early brain injury

suggesting that TNF-α may be involved in the pathological process of early brain injury after subarachnoid hemorrhage by regulating the expression of MMP-9.