The Effects Of Modified Bu-Wang Powder On Learning And Memory In Vascular Dementia Rat Models And Its Synaptic Plasticity Mechanism

Objective:Vascular Dementia(VaD)is a cognitive dysfunction disease that seriously affects human health.VaD has become the second common cause of dementia,with increasing incidence of cerebrovascular disease,the research on which has become one of the focuses.It is meaningful to explore and clarify the treatment and preventive measures of VaD.The main purpose of this research including:1.To observe the effects of Modified Bu-Wang Powder(MBWP)on learning and memory ability of VaD model rats;2.To study the effect of MBWP on the morphology and synaptic structure of hippocampal neurons in VaD rats;3.To explore the effects of MBWP on synaptic plasticity of hippocampus in VaD model rats;4.To study the mechanism of MBWP on prevention and treatment of VaD.Methods:1.200 male SD rats were equally divided into sham control group,VaD model group,the low dose MBWP group(MBWP low),medium dose MBWP group(medium MBWP)and high dose MBWP group(high MBWP),40 rats in each group;2.The Two-vessel occlusion method was used for VaD model,and then administered with MBWP orally for four consecutive weeks;3.The learning and memory ability was tested by Morris water maze,Y maze,shuttle box behavioral tests to evaluate the effect of MBWP on VaD rats;4.The synaptic plasticity in the hippocampus of rats was tested by the long-term potentiation(LTP);5.The pathologic changes of nerve cells in the hippocampus were observed by hematoxylin and eosin stain(HE);6.To observe the ultrastructural changes of the hippocampus by transmission electron microscopy;7.The levels of GAP43,SYN,PSD-95,MAP-2,BDNF and TrkB mRNA in the hippocampus was assessed by RT-PCR;8.The expression of GAP43,SYN,PSD-95,MAP-2,BDNF and TrkB in the hippocampus was analyzed by Western blotting;9.SPSS 24.0 and Graphpad prism 7.0 software were used to analyze data and make statistical analysis charts.Results:1.In place navigation test of Morris water maze,compared with Sham control,the average escaping latency of VaD model was greatly prolonged,and the ability to learn spatial markers was reduced from the third day(P < 0.01).Compared with VaD model,the escape latency of the rats in the MBWP low,medium and high groups was significantly shortened.The MBWP high group had the biggest influence on improving the spatial learning ability of VaD model rats.In the space exploration experiment,compared with the Sham control,the time of staying in the target quadrant was significantly reduced in the VaD model(P < 0.001),suggesting that the spatial memory of VaD rats was seriously impaired.The time staying in the target quadrant of MBWP medium and high groups was significantly prolonged,and the differences were statistically significant(P < 0.001).There was no significant differences in the time to reach the visual platform and swimming speed in each group(P > 0.05),considering that surgical operation and medical treatment had no effect on the visual acuity and swimming ability of the rats.2.In the Y maze test,compared with the Sham control,the percentage of correct spontaneous alternations of the VaD model was significantly reduced(P < 0.001),indicating that the working memory ability of the VaD model rats was seriously impaired.On contrary,the MBWP medium and high groups could improve the percentage of correct spontaneous alternations,and the differences were statistically significant(P < 0.05,P < 0.001),indicating that the MBWP could obviously improve the spatial working memory ability of VaD model.There were no differences in the total number of arm entries among the five groups(P > 0.05),showing that surgical operation and medical treatment have no influences on the exercise capacity and exploring desire of the rats.3.In the shuttle box test,compared with the Sham control group,the percentage of active avoidance scores of the VaD model was significantly lower(P < 0.001),and the active avoidance latency of the VaD model was significantly prolonged(P < 0.001),declaring that the learning and memory ability of VaD model rats to avoid noxious stimulation is severely impaired.Compared with the VaD model,the percentage of active avoidance scores of the rats in MBWP medium and high groups was significantly higher(P < 0.001),and the active avoidance latency was significantly shorter(P < 0.001),the learning and memory ability to avoid noxious stimuli was notably improved by MBWP.Moreover,the MBWP high group had the best effect on VaD model.4.In the LTP experiment,compared with the Sham control,the percentage of f-EPSP slope in the VaD model group was significantly dropped,LTP was significantly suppressed(P < 0.001),suggesting that the hippocampal synaptic plasticity was greatly damaged.MBWP medium and high groups reversed the suppression of LTP in the VaD model group(P < 0.001).MBWP can improve synaptic plasticity of rats in VaD model.5.The histological changes in the hippocampus of rats were observed by HE staining.In the hippocampus of rats in VaD model group and MBWP low group,the number of neurons was decreased,the cell volume was reduced,the karyopyknosis was observed,and the arrangement was disordered.While,in hippocampus of MBWP medium and high groups,the number of hippocampal neurons significantly increased,the arrangement became neat,and the abnormal cells was decreased.6.The ultrastructural changes in the hippocampus of rats were observed by transmission electron microscopy.The results showed that in the hippocampus of VaD model group,the synaptic structure was destroyed,the number of synapsis was reduced,the synaptic structure was incomplete,the synaptic gap was enlarged and the dense substance on the postsynaptic membrane was thinner.Compared with the VaD model group,with the increasing dose of MBWP,the synaptic structure in the hippocampus gradually became more and more complete,the synaptic gap changed from large to small,and the dense substance on the postsynaptic membrane changed from less to more.7.The changes of synaptic proteins involving GAP43,SYN,PSD-95 and MAP-2 in the hippocampus of rats were detected by molecular biology techniques.The results showed that transcription and expression levels of GAP43,SYN,PSD-95 and MAP-2 in the hippocampus of the VaD model group were significantly lower than those in the Sham control group(P < 0.05).Compared with the VaD model group,the transcription and expression levels of GAP43,SYN,PSD-95 and MAP-2 in the hippocampus gradually increased with the increasing dose of MBWP(P < 0.05).8.The changes of BDNF and TrkB in the hippocampus of rats were detected by molecular biology techniques.The results showed that the transcripts and expression levels of BDNF and TrkB in the hippocampus of the model group were significantly lower than those in the sham control group(P < 0.05).Compared with the VaD model group,the transcription and expression levels of BDNF and TrkB in the hippocampus increased with the increasing dose of MBWP(P < 0.05).Conclusion:1.MBWP could significantly improve the learning and memory ability of VaD model rats dose-dependently.2.MBWP can improve the number and ultrastructure of synapse in VaD model rats.3.MBWP could improve the synaptic plasticity in the hippocampus of VaD model rats dose-dependently.4.MBWP may improve the transcription and translation levels of GAP43,SYN,PSD-95 and MAP-2 in the hippocampus of VaD model rats.5.MBWP may up-regulate the signaling pathway of BDNF-TrkB in the hippocampus of VaD model rats.This suggests that,MBWP may have positive influence on the treatment of VaD.This subject was funded by the Shanxi Graduate Education Innovation Project “Effects of Modified Bu-Wang Powder on Learning and Memory in Vascular Dementia Rat Models and its Synaptic Plasticity Mechanism(No.2018BY070)”.