Effects Of Environmental Enrichment On Learning And Memory Ability And The Expression Of Bdnf And Synaptophysin In Hippocampus Of Neonatal Rats With Hypoxic-ischemic Brain Damage

Objective To explore the effects of environmental enrichment（EE）with different strength on learning and memory ability and the expression of brain-derived neurotrophic factor（BDNF）and Synaptophysin in hippocampus of neonatal rats aged 7 days（equivalent of the neonatal period of human）with hypoxic-ischemic brain damage.Then,seeking the effectiveness and mechanism of the early environmental enrichment intervention and providing possible theoretical basis for Clinical rehabilitation programme of children with HIBD.Method40 Wistar neonatalmale rats aged 7 days were randomly divided into environmental enrichment intervention group for 6 hours（6h EE）（n=10）,environmental enrichment intervention group for 12 hours（12h EE）（n=10）,model group（Model）（n=10）and sham group（Sham）（n=10）.6h EE、12h EE and Model group were performed with hypoxic-ischemic brain damage.The 6h EE and 12 h EE group received environmental enrichmentstimuli for 6h and 12 h respectively,once a day for 14 days.Learning and memory of the rats was tested by Morris water maze.The expression level of BDNF and Synaptophysin in hippocampus was determined with Western blot.Result1、In the Morris water maze,the escape latency of all groups gradually reduced with the increase of training days,but we did not observe significant difference in the escape latency between each group（F=0.2369,P>0.05）.2 、 In the Morris water maze,on the 5th day of probe trail,there was no statistically significant difference when rats Looking for platform in the target quadrant,compared with in other quadrants in Model group（P>0.05）;The other three groups were statistically significant（P<0.05）.3、On the 7th day of probe trail in the Morris water maze,All rats Remembered the location of the platform.The rats in the 6h EE group（（（?）± s）6h EE=38.132 ± 2.876,P<0.001）、12h EE group（（（?）± s）12h EE =45.526 ± 2.648,P<0.001）and Model group(（（?）± s）_Model=30.702 ± 3.819,P<0.001)spent less time in the target quadrant and showed a significantly reduction of BDNF(（（?）± s）6h EE=0.529 ± 0.038,P<0.001;（（?）± s）12h EE =0.660 ± 0.034,P<0.01;（（?）±s）_Model=0.225 ± 0.015,P<0.001)and Synaptophys(（（?）± s）6h EE=0.889 ± 0.027,P<0.001;（（?）±s）12h EE=1.114 ± 0.037,P<0.05;（（?）± s）_Model=0.672 ± 0.057,P<0.001)in the hippocampus than the Sham group（（（?）± s）time=54.400±3.152;（（?）± s）BDNF=0.803 ± 0.026;（（?）± s）Synaptophysin=1.347 ± 0.092）.4、 In the 6HEE group and 12 h EE group,the rats significantly increased the time spent in target quadrant（P6h EE<0.01;P12h EE<0.001）and aggrandized the expression of BDNF（P6h EE<0.001;P12h EE<0.001）and Synaptophysin（P6h EE<0.05;P12h EE<0.001）in hippocampus compared with the Model group.5 、 Moreover,12 h EE group have a better performance than 6h EE group in the Space exploration（P<0.01）and the expression of BDNF（P<0.01）and Synaptophysin（P<0.05）.Conclusion Environmental enrichment was helpful for improving learning and memory ability in neonatal rats with hypoxic-ischemic brain damage,which may associate with increasing the expression of BDNF and Synaptophysin in hippocampus.