| Objectives:Vascular dementia(VD) has become a common and frequent disease in middle- aged and aged people.The prominent clinical characteristics of VD are that learning, memory and other cognitive function decline,with or without symptoms and sign of neurologic impairment.At present,the pathogenesis of VD has not been illustrated clearly,and has not been effectively dealed with,either.Therefore,it's an important subject in medicine field to explore the pathogenesis of VD and make a reasonable therapeutic regimen.One of the VD etiopathogenisis may be related to the ischemia and hypoxia caused by Chronic cerebral hypoperfusion.The so-called Chronic cerebral hypoperfusion is a pathologic status of pathological status of chronic ischemic nerve system injury with long term low perfusion brain that lower than threshold caused by hypertension and cerebral artery sclerosis.Chronic cerebral hypoperfusion is a common pathological course of the developing of vascular dementia,Alzheimer's disease, Bingswanger's disease,and so all.A large number of studies have shown that cognitive fuction can be impaired under hypoperfusion and hypometabolism.And the disorder of free radical metabolism in brain may be one of the major possible mechanism,which results in impairment of cerebral texture and microvascular system.Mitochondria is the main organelle which not only produce oxygen free radicals but also are the main sites of energy metabolism.So the internal structure of mitochondrial are the primary objective impaired by oxygen free radicals. Therefore,the abnormality of mitochondrial structure and function may play a key role in the pathogenesis of VD.In recent years,which has attracted extensive attention, the clinical use of dl-n-butylphthalide(dl-NBP) on cerebral ischemia has a neuroprotective effect.DL-NBP are synthetic drugs derived from natural chemicals.Pharmacological experiments show that there is good anti-cerebral ischemia and cerebral protection,especially for acute focal ischemic neuronal mitochondrial structure and function,which play a protective role.But most studies about dl-NBP's neuroprotective effect have only focused on acute cerebral ischemia model at home and abroad,while the researches about its effect on chronic cerebral hypoperfusion model have still lacked.But most studies about dl-NBP's neuroprotective effect have only focused on acute cerebral ischemia model at home and abroad,while the researches about its effect on chronic cerebral hypoperfusion model have still lacked.This experiment mimicried human chronic cerebral hypoperfusion by the ligation of bilateral carotid arteries in Sprague -Dawley male rats,to observe their changes of learning and memory by the water maze test,to observe morphological changes of mitochondria by transmission electron microscope to observe ATPase activity,SOD activity and MDA content in mitochondria by spectrophotometric determination,and at the same time to explore the effect of dl-NBP,a new type of neuroprotective medicamentum,on them. We provided a new evidence for clinic treating vascular cognitive disorder as well as revealed the pathogenesis of VD.Methods:55 Sprague-Dawlay rats,3～4months old,280～340 g in weight,were randomly divided into sham group(n=10), saline group(n=15),dl-NBP low dose treatment group(n=15) and dl-NBP high dose treatment group(n=15).Saline group and treatment group were followed permanent occlusion of bilateral common carotid arteries(2-VO) accoding to de la Torre's method.Sham group was handled as Saline and treatment group except not ligating bilateral common carotid arteries.After 4 weeks following the operation,dl-NBP low dose treatment group were injected dl-NBP(4mg/kg/d) through abdomen cavity for 4 weeks.And dl-NBP high dose treatment group were injected dl-NBP(12mg/kg/d) through abdomen cavity for 4 weeks too.Saline group were injected isodose saline.Congnitive ability of all Survival rats was evaluated by water maze test after 8 weeks.After the last water maze test,brain tissue in temporal lobe cortex of 2 rats of every group were taken out,put into solution of 4%glutaral,after a series treatment,observed and photoed under transmission electron microscope.The remaining animals were fasted 12 h,decapitated,taken out brain tissue on ice,extracted mitochondria,and suspended them in EDTA sucrose- Tris-HCl buffer solution.Protein level was measured by Coomassie brilliant blue method.Protein concentration adjust to 1mg/ml.ATPase activity,SOD activity and MDA content in mitochondria were measured separately.One-way analysis of variance was carried out with SPSS 13.0 statistics software,LSD-t test was used to compare the differences among the groups.P＜0.05 meant statistical significance.Results:(1):The survival condition of each group:0 died in the sham group.5 rats died in the saline group and 8 weeks group.The death rate was 33.3%.4 and 5 rats died respectively in dl-NBP low dose treatment group and dl-NBP high dose treatment group.The death rates were 26.7%and 33.3% respectively.All survival rats of each group were as study objects.(2):Water maze test:Learning and memory performances of rats decreased obviously in saline group,showing escape latency(EL) extended which were clearly higher than sham group(p＜0.05).Learning and memory performances in dl-NBP low dose treatment group and dl-NBP high dose treatment group improved significantly(p＜0.05), compared with saline group.Learning and memory performances in dl-NBP low dose treatment group and dl-NBP high dose treatment group still decreased but not notablely,if compared with sham group(p＞0.05).Learning and memory performances in dl-NBP high dose treatment group didn't improve notablely,compared with dl-NBP low dose treatment group.(3):the changes of mitochondria ultrastructure:In sham group mitochondrial ultrastructure is observed clearly,and there is no obvious abnormalities.In saline group the majority of mitochondrial cristae disappearing,mitochondrion edema,the double-unit membrane of some mitochondrium disappearing, rough endoplasmic reticulum degranulation,neuronal cytoplasmic edema,Organelle decreased significantly.In dl-NBP high dose treatment group mitochondria are close to normal.In this group lysis of mitochondrial cristae and vacuolization of mitochondria were not observed but in some of mitochondria there were some reversible injury,such as rough endoplasmic reticulum cavity to expand and mitochondrial hypertrophy.In dl-NBP low dose treatment group most of mitochondrial morphology are regular,the mitochondrial cristae are complete.(4) The results of ATPase activity in mitochondria: Compared with sham group,ATPase activity in mitochondria significantly decreased in saline group(p＜0.05).Compared with saline group,ATPase activity in mitochondria increased in dl-NBP low dose treatment group(p＜0.05).Compared with saline group,ATPase activity in mitochondria significantly increased in dl-NBP high dose treatment group(p＜0.05).After dl-NBP treatment,the ATPase activity increased.Compared with dl-NBP low dose treatment group,ATPase activty of dl-NBP high dose treatment group increased but not notablely(p＞0.05). (5) The results of SOD activity and MDA content in mitochondria:Compared with sham group,SOD activity in mitochondria decreased in saline group,and MDA content increased(p＜0.05).Compared with saline group,SOD activity in mitochondria increased in dl-NBP low dose treatment group,and MDA content decreased(p＜0.05).Compared with saline group,SOD activity in mitochondria significantly increased in dl-NBP high dose treatment group,and MDA content decreased(p＜0.05).After dl-NBP treatment,the SOD activity increased and MDA content decreased(p＜0.05). Compared with dl-NBP low dose treatment group,SOD activty of dl-NBP high dose treatment group increased more,and MDA decreased but not notablely(p＞0.05).Conclusions:(1)This experiment successfully established chronic cerebral hypoperfusion model by ligation of bilateral common carotid arteries in rats.Water maze test verified that model rats existed learning and memory disorder,which further confirmed that the model is dependable.Mitochondria ultrastructure of the chronic cerebral hypoperfusion rats has notablely changed,which was observed by transmission electron microscope.(2) The SOD activity decreased and MDA content increased in mitochondria of the chronic cerebral hypoperfusion rats,Which shows that mitochondrial oxidative damage may be one of the pathogenesis of VD.(3) The ATPase activity increased in mitochondria of the chronic cerebral hypoperfusion rats,Which shows that energy metabolism disorder may be one of the pathogenesis of VD.(4) The mitochondria structure and function in Rats with Chronic Cerebral Hypoperfusion can be protected by dl-NBP.
|
PDF Full Text Request