| Background and objective:China is facing up to aging population.The morbidity ratio of cerebrovascular disease increases with years.Ischemic stroke may leads to dementia. Hyperbaric oxygenation physically dissolves extra oxygen into the blood plasma.HBO(Hyperbaric Oxygenation) delivers many times as much physically dissolved oxygen to tissues as breathing room air.This promotes formation of new capillaries into wound areas,and sufficient oxygen tensions to meet the needs of ischemic tissues.Time window of HBO therapy plays an important role in treating ischemic stroke;most experiments concluded that HBO should be applied within 6 hours after ischemia.Researchers seldom compare different time window of HBO and it's long-term effect.This experiment is to investigate the effect of HBO therapy at different time windows on learning and memory function of model rats suffering from ischemia-reperfusion injury,evaluate the long-term therapeutic effect and explore the possible neural protective mechanism.Method:40 male Wistar rats were randomly assigned to 4 groups. Focal cerebral ischemia-reperfusion(I/R)injury rats model was induced by reversible middle cerebral artery occlusion(MCAO). HBO treatment was administered at 6 or 24 hours after reperfusion respectively in earlier(EHBOT)or delayed therapy (DHBOT) groups.Neurological deficits were assessed after ischemia and before rats were kill.The spatial learning and memory abilities were evaluated by the Morris water maze test. The infarct volume ratio of each group was measured by 2,3, 5-triphenyltetrazolium chloride(TTC) staining.The counting of reaction positive neurons of iNOS,CHAT,and apoptosis related Bcl-2,Bax proteins in hippocampal CA1 region was detected by using immunohistochemistry staining technique.Result:Of rats in EHBOT group,compared with that in ischemia-control group, the learning and memory abilities improved and the brain infarct volume ratio diminished markedly(P＜0.01).In counting of reaction positive neurons in hippocampal CA1 region,results showed that the number of choline acetyl transferase(ChAT) and Bcl-2 positive neurons increased significantly(all P＜0.01). The iNOS reaction positive neurons decreased obviously while the Bax expression was no marked different.Similar changes occurred in DHBOT group,but the number of reaction positive neurons of iNOS and Bax was no marked different.Conclusion:Both early and delayed HBO therapy showed a neural protective effect against transient MCAO induced long-term brain morphological and histological deficits and spatial learning and memory dysfunction.Possible mechanism may include increasing oxygen supply to the ischemic neurons, inhibiting neural apoptosis caused by ischemia and alleviating ChAT positive neurons damage.Delayed but multiple HBOT is also useful,more researches are needed.Significance:HBOT is widely used to treat acute cerebral ischemic stroke,most RCTs affirmed its security but the exact effect is still uncertain.This animal experiment affirms HBOT's effect and suggests HBOT should be applied within 6 hours after cerebral ischemic stroke.Delayed but multiple HBOT is still useful. |
