Objective    To observe the relation between the expression of MMP-9 and neuronal apoptosis of hippocampus and investigate the mechanism of MMP-9 involved in early brain injury after subarachnoid hemorrhage (SAH).     Methods    Totally 108 adult male SD rats were randomly divided into 2 groups

the sham-operation group and SAH group. The SAH model was induced by injecting 300  μl of autologous arterial blood into the subarachnoid space near the circle of Willis via a cannula in an artificial hole between the olfactory bulb and frontal lobe. Activity of MMP-9 in the hippocampus were examined at 6

12

24

48 and 72 h by gelatin-containing SDS-PAGE zymography. The changes of laminin and  the component of extracellular matrix were examined by immunohistochemistry. Meanwhile

the hippocampal neuronal apoptosis were measured by TUNEL.     Results    (1) The zymography showed the activity of MMP-9 was increased dramatically at 12 h and reached the peak at 24 h

then decreased gradually and to the lowest level at 72 h

but was still higher than that of sham group (P0.01). (2) The immunohistochemical staining indicated that hippocampal laminin began to decrease at 12 h

and to the lowest at 24 h

then increased at 48 h. But compared with the level of sham group

laminin at 72 h after SAH was still lower (P0.01). (3) The number of apoptotic neurons of the hippocampus was increased at 12 h after SAH

reached a peak at 24 h and began to decrease at 48 h. The number of  at 72 h after SAH was still higher than that at sham group (P0.01).     Conclusion    MMP-9 in the hippocampus of rats after SAH may be involved in the pathological progression of early brain injury

through degrading laminin which led to anoikis in rat hippocampal neurons.