| Objectives: The last decade has witness the increased incidence ofvascular dementia (VD). It has become the main cause of threathing thehealth in the elders and done great harm to the society and family. Therefore, itis significant to study the pathogenesis of VD.It is reported that brain derived neurotrophic factor (BDNF) is a cytokinewhich can provide nutrition to the neurons. Its expression is increased incerebral ischemia. It can evoke the PI3K-Akt cell signal pathway by bindingwith receptor tyrosine kinases B (TrkB). The active Akt can combined with itssubstrate-glycogen synthase kinase-3(GSK3), resulting its malfunction toresist apoptosis. But until now the exact effect on VD is still unknown. In thisstudy, the changes of pathology and expression of Akt、GSK-3β protein inhippocampus will be examed to explore the pathogenesis of VD.Methods: The study inculds three parts1The C57Bl/6mice were subjected to20min ischemia and10min reperfusionby ligating the bilateral common carotid arteries. The ischemia-reperfusion isrepeated three times to establish the VD model. The mice were divided intonormal group, sham group and model group. In15th/16thday,29th/30thday and42th/43thday after operation, the learning and memory function of each groupwere evaluated through water maze test and step-down test. After tests, HEstaining is used to observe the changes of hippocampal tissue.2The expression of Akt, p-akt protein in hippocampus were observed throughthe techniques of Western-blot.3The expression of GSK3β, p-GSK3β protein in hippocampus were observedthrough the techniques of Western-blot. Result:1The weight changes of mice3days after operationThe weight of VD mice was decreased obviously after operation, and itrecovered to normal level3days after operation.2Water maze test2.1In15th,29thand43thdays after operation, the results of learning functionrevealed that:2.1.1The swimming time: The time between normal group and sham groupwere approximately the same; model group had longer time compared withsham group(P<0.05).2.1.2The numbers of error: The number between normal group and shamgroup were approximately the same; model group had more errors comparedwith sham group(P<0.05).2.2In16th,30thand44thdays after operation, the results of memory functionrevealed that:2.2.1The swimming time: The time between normal group and sham groupwere approximately the same; model group had longer time compared withsham group(P<0.05).2.2.2The numbers of error: The number between normal group and shamgroup were approximately the same; model group had more errors comparedwith sham group(P<0.05).3Step-down test3.1In15th,29thand43thdays after operation, the results of learning functionrevealed that:3.1.1The response time: The time between normal group and sham groupwere approximately the same; model group had longer time compared withsham group(P<0.05).3.1.2The numbers of error: The number between normal group and shamgroup were approximately the same; model group had more errors comparedwith sham group(P<0.05).3.2In16th,30thand44thdays after operation, the results of memory functionrevealed that: 3.2.1The latency time: The time between normal group and sham group wereapproximately the same; model group had shorter time compared with shamgroup(P<0.05).3.2.2The numbers of error: The number between normal group and shamgroup were approximately the same; model group had more errors comparedwith sham group(P<0.05).4HE staining of hippocampus in each group4.1Normal group: There were great of pyramidal cells in the area ofhippocampus and they ranged tightly and in order. The profile was clear. Thenucleus were circinal and big, with clear nucleolus. The number of normalneuron was(115.13±1.92).4.2Sham group: There were great of pyramidal cells in the area ofhippocampus and they ranged tightly and in order. The profile was clear. Thenucleus were circinal and big, with clear nucleolus. The number of normalneuron2,4and6weeks after operation were (115.23±2.14),(114.92±2.08)and (114.38±2.76).4.3Model group：There were less pyramidal cells that ranged loosely in thearea of hippocampus. Their nucleus appeared pyknosis and became small,with no clear nucleolus. The gliocytes were over expressed4and6weeks afteroperation. The number of normal neuron2,4and6weeks after operation were(94.67±1.97),(34.92±2.90) and (69.96±2.37), lower than shamgroup(P<0.05). Among those the most damaged group were the one that4weeks after operation. There were only a few neurons alive, and the number ofnormal cells were lower than that of2and6weeks after operation (P<0.05).5Protein expression of Akt, p-Akt in hippocampus tested by Western-blot5.1The expression of Akt protein:The total protein expression of Akt was approximately the same amongnormal group, sham group and model group. And it was equal in different timepoints after operation.5.2The expression of p-Akt protein:The expression of p-Akt between normal group and sham group were approximately the same. Model group had more expression. It was increasedapparently4weeks after operation.6Protein expression of GSK3β, p-GSK3β in hippocampus tested byWestern-blot6.1The expression of GSK3β protein:The total protein expression of GSK3β was approximately the sameamong normal group, sham group and model group. And it was equal indifferent time points after operation.6.2The expression of p-GSK3β protein:The expression of p-GSK3β between normal group and sham group wereapproximately the same. Model group had more expression. It was increasedapparently4weeks after operation.Conclusion:1The study provided a perfect VD mice model which had the similarabnormality of learning and memory function of VD patients and obversed theobvious damage in hippocampal tissue by HE straining. It is suggest that thismodel might successfully imitate the cognitive impairment of VD in clinic andis feasible to study the VD.2In VD mice, the expression of total Akt protein was approximately the samein the three groups, but the expression of p-Akt protein was increasedsignificantly. It is suggest that active Akt might play a protect role in resistingthe apoptosis after repeated cerebral ischemia and reperfusion.3In VD mice, the expression of total GSK3βprotein was approximately thesame in the three groups, but the expression of p-GSK3β protein wasincreased significantly. It is suggest that p-GSK3βparticipate in the ischemiareperfusion,and the active Akt might depressed the ability of GSK3β, so it canplay an important role in neuron survival and improving cognition. |
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