The Role Of MiR-9 In The Improvement Of Learning And Memory Ability Of Rats With Hypoxic-ischemic Brain Damage By Sodium Ferulate

Objective:To investigate the regulatory effect of miR-9 on NMDARI and NgRl in HIBD rats which was based on the hypoxic-ischemic brain damage(HIBD)animal model of newborn ratsMethods:7-day-old SD neonatal rats were randomly divided into sham group(Sham),hypoxic-ischemic brain damage group(HIBD),sodium ferulate treatment group(HIBD+SF),PBS group(HIBD+PBS)and miR-9 inhibition group(HIBD+LNA).HIBD model was established by the ligation of left common carotid artery and hypoxia in a 3 gas incubator containing 8%O2 and 92%N2 at 35? for 2 hours,while,the rats in sham group just underwent the isolation of left common carotid artery without ligation and hypoxia.After 48 hours of modeling,the left brain of rats in sham group and HIBD group were taken to observe the edema and measure the water content,and TTC staining was used to detect the area of cerebral infarction and HE staining was used to detect neuron necrosis.After 2 weeks of molding,the rats of(HIBD+SF)group were intraperitoneally injected with sodium ferulate for 5 consecutive days,while rats of(HIBD+PBS)group and(HIBD+LNA)group were administered left intracerebroventricular injection with 2?l of PBS and 2?l of LNA-miR-9,respectively.Subsequently,Morris water maze was used to detect the spatial learning and memory ability of P30 rats.Finally,the left hippocampal tissues of P26 rats were frozen with liquid nitrogen.Then the protein expressions of NMDAR1 and NgRl in the left hippocampal neurons of each group were detected by Western blot,and the expressions of miR-9,NMDAR1 mRNA and NgRl mRNA in the left hippocampal tissue of each group were detected by real time RT-PCRResults:1.Molding resultsAfter 48 hours of modeling,the left brain tissue of HIBD group was obviously pale and edematous,while that of sham group was not.The water content of the left brain tissue in HIBD group was significantly higher than that in sham group(P<0.05).The results of TTC staining showed that there was obvious infarct in the left brain tissue of HIBD group(P<0.05),but there was no infarct in the brain tissue of sham group.The HE staining results showed that the left hippocampal CA3 area and the left cerebral cortex tissue structure in the HIBD group were loose,with interstitial edema,widened spaces around capillaries,degeneration and necrosis of neurons and glial cells with infiltration of inflammatory cells.The intercellular space widened and appeared vacuolated,with deep staining of the nucleus of the nerve cells,shrinking of the nucleus,disappearance of nucleoli,disappearance of cytosolic Nissl bodies.However,there was almost no pathological change in the sham group2.Spatial learning and memory ability of rats in each groupOrientation and navigation experiment:Compared with the Sham group,the escape latency of the HIBD group was significantly longer(P<0.05);compared with the HIBD group,the escape latency of(HIBD+SF)was significantly shorter(P<0.05);compared with the(HIBD+PBS)group,the escape latency of(HIBD+LNA)group was significantly shorter(P<0.05)Space exploration experiment:Compared with the sham group,the target quadrant stay time of HIBD group was significantly longer(P<0.05),and the trajectory route was more diffuse;compared with HIBD group,the target quadrant stay time of(HIBD+SF)group was significantly shorter(P<0.05),and the traJ ectory route was more concentrated in the target quadrant;compared with(HIBD+PBS)group,the target quadrant stay time of(HIBD+LNA)was significantly shorter(P<0.05),and the trajectory route was more concentrated in the target quadrant3.Expression of miR-9 in left hippocampus of rats in each groupCompared with sham group,the expression of miR-9 in HIBD group was significantly up-regulated(P<0.05);compared with HIBD group,the expression of miR-9 in(HIBD+SF)group was significantly down-regulated(P<0.05);compared with(HIBD+PBS)group,the expression of miR-9 in(HIBD+LNA)group was significantly down-regulated(P<0.05)4.The mRNA expressions of NMDAR1 and NgR1 in left hippocampus of rats in each groupCompared with sham group,the mRNA expressions of NMMAR1 and NgR1 in HIBD group was significantly up-regulated(P<0.05);compared with HIBD group,the mRNA expressions of NMDAR1 and NgR1 in(HIBD+SF)group was significantly down-regulated(P<0.05);compared with(HIBD+PBS)group,the mRNA expressions of NMDAR1 and NgRl in(HIBD+LNA)group was significantly down-regulated(P<0.05)5.The protein expressions of NMDAR1 and NgRl in left hippocampus of rats in each groupCompared with sham group,the protein expressions of NMDAR1 and NgRl in HIBD group was significantly up-regulated(P<0.05);compared with HIBD group,the protein expressions of NMDAR1 and NgRl in(HIBD+SF)group was significantly down-regulated(P<0.05);compared with(HIBD+PBS)group,the expressiosn of NMDAR1 and NgRl in(HIBD+LNA)group was significantly down regulated(P<0.05)Conclusion:Hypoxia-ischemia lead to the impairment of long-term spatial learning and memory in rats.Sodium ferulate may inhibit the expression of NMDAR1 and NgRl by down regulating miR-9,and then decrease the excitatory toxicity of NMDAR and the inhibitory effect of NgRl on axon growth,thus improving the learning and memory ability of HIBD rats.