Objective         To observe the neuroprotective effect of hyperbaric oxygen preconditioning (HBOP) in rats after middle cerebral artery occlusion (MCAO)

and to investigate the effect on osteopontin (OPN) expression.       Methods        Seventy-two Sprague-Dawley rats were randomly and equally divided into 4 groups including a sham group

a HBOP+sham group

a simple MCAO group and a HBOP+MCAO group (n=18). The neurological deficits and cerebral infarction volume were detected in the rats at 12 h after permanent MCAO. The pathological changes of ischemic regions were observed under a light microscope by HE staining

and the expression of OPN in ischemic regions was determined by Western blotting.       Results       The scores of neurological deficits at 12 h after MCAO were 0 in the sham and HBOP+sham groups

3.80±0.79 in the simple MCAO group

and 2.50±0.97 in the HBOP+MCAO group. The scores of balance ability at 12 hours after MCAO were 5 in the sham and HBOP+sham groups

1.50±1.08 in the simple MCAO group

and 2.70±2.95 in the HBOP+MCAO group. The proportions of cerebral infarction volume at 12 hours after MCAO were 0 in the sham and HBOP+sham groups

49.22±7.07 in the simple MCAO group

and 41.96±3.15 in the HBOP+MCAO group. Compared with the simple MCAO group

the score of neurological deficits reduced significantly (P0.05)

the score of balance ability increased significantly (P0.05)

and the proportion of cerebral infarction volume was significantly lower in the HBOP+MCAO group at 12 h after MCAO (P0.05). The pathological injury of brain tissues in ischemic region was significantly relieved

and the expression of OPN was upregulated in the HBOP+MCAO group.       Conclusion       HBOP plays a neuroprotective role in rats after MCAO

and the mechanism may be associated with the upregulation of OPN.