Effect of hyperbaric oxygen preconditioning on expression of Nogo mRNA,Nogo-A and NgR protein in the cerebral cortex after acute global cerebral ischemia-reperfusion injury in aged rats

Abstract

Objective To investigate the effect of hyperbaric oxygen preconditioning(HOP)on expression of Nogo mRNA,Nogo-A and NgR protein in the cerebral cortex after acute global cerebral ischemia-reperfusion(I/R)injury in aged rats.Methods Forty-two aged male SD rats aged 14 months weighing 480-530 g were randomly divided into 4 groups: group Ⅰ control(group C,n = 6);group Ⅱ HOP(n = 12);group Ⅲ cerebral I/R(n = 12)and group Ⅳ HOP+I/R(n = 12).Global cerebral I/R was induced by 4-vesasl occlusion method described by Pulsinelli.Bilateral vertebral arteries were permanently occluded by cauterization,aad bilateral carotid arteries were occluded for 10 min.Successful induction of cerebral ischemia was confirmed by bilateral dilated pupils unresponsive to light and EEG changes.In group Ⅱ and Ⅳ the animals received 1 h hyperbaric oxyyen at 2 absolute atmospheric pressure per day for 5 consecutive days.In group Ⅳ(HOP+I/R)global cerebral I/R was induced at 24 h after last hyperbaric oxyyen treatment.Six animals in each group were killed at24 h after I/R in each group and their brains were removed for detection of Nogo mRNA expression(by Q-PCR)and expression of Nago-A and NgR protein(by Western blot)in cerebral cortex.Cognitive function was determined at 5 days after cerebral ischemia using Morris Water Maze in the other animals.Results The learning ability and memory were significantly decreased while the expression of Nogo mRNA and Nogo-A protein was significantly increased in group Ⅲ(I/R)and Ⅳ(HOP+I/R)as compared with control group.HOP significantly ameliorated the cerebral I/R-induced decrease in learning ability and memory and increase in Nogo mRNA and Nogo-A protein expression.Conclusion Hyperbaric oxyyen preconditioning can ameliorate acute global cerebral I/R injury-induced cognitive impairment by decreasing Nogo mRNA and Nogo-A protein expression in the brain. Key words: Hyperbaric oxygenation; Ischemic preconditioning; Reperfusion injury; Brain; Aged; Nogo; Nogo-A; NgR