Abstract: To investigate the effect of hyperbaric oxygen(HBO)on caspase-3 activity, we devided 200～250 g Sprague-Dawlay rats into three groups: the ischemia/ reperfusion group(I/R), the group treated by HBO and the sham operated group(Sham-O)as the control. Global brain ischemia was induced by using a modified four vessel occlusion model originally described by Pulsinelli and Buchan. Cortex of parietal lobe was obtained and homogenized respectively at reperfusion time points of 6 h, 24 h, 48 h and 96 h after 20 minutes of ischemia. Then caspase-3 activity was measured by cleavage of the colorimetric substrate of DEVD-ρNA. Although both caspase-3 activity of the HBO group and I/R group were not statistically different from the Sham-O group at reperfusion time point of 6 h,the HBO group was higher than the I/R group(P<0.05). Both the HBO group and I/R group were higher than the Sham-O group(P<0.05)at 24 h of reperfusion, but there was no statistical difference between the former two groups. At reperfusion time points of 48 h and 96 h, the HBO and I/R group were higher than Sham-O group, but there was no statistical difference. And there was no statistical difference between the former two groups either, which indicated that caspase-3 activity had decreased to normal levels. The results of above indicated that caspase-3 was activated after global ischemia/reperfusion. HBO treatment at early time may aggravate this activation, but after several times of HBO treatment, this promotion effect becomes indistinct.

Key words: hyperbaric oxygen|cerebral ischemia|reperfusion|caspase-3|apoptosis