| Objective:With the proportion of the elderly in the population increases and the survival rate of salvaging the patients with cerebral vascular disease(CVD) rises. the mental and intelligent handicaps caused by CVD significantly increased. Vascular dementia(VD) which is seriously harming the body and the mentality of the elderly, is an intelligent dysfunction syndrome, acquired and durative, resulted from all sorts of CVD.It is an important cause of senile dementia. Though the incidence of VD is lower than that of Alzheimer′s disease (AD),but on the actual clinical meaning, VD possess more preventive and treatment value than AD.Hence, more attention has been focused on VD recently.Recent studies suggest that chronic hypoperfusion of cerebral blood flow(CBF)in the forebrain maybe one of a major causes for VD, and the central cholinergic systerm have close relationship with the cognitive function. The basal forebrain cholinergic projection neurous are much vulnerable to ischemia and anoxia, with lead to decrease synthesizing of acetylcholine presynapse and expression of acetylcholine receptors postsynapse. Therefore the muscarine and nicotine signal transduction pathway associated with isoforms of receptors may disorder and influence the phosphorylation protein kinase C (PKC) downstream,which will influence the synapse plasticity, neural network and eventually the whole cognitive function. As a classics drug, donepezil hydrochloride has been used widely in the treatment of VD, but the pharmacological mechanism of treating VD is still in discussion. The VD mice models were established in the experiment, the changes of PKC in hippocampus were observed and the mechanism of donepezil hydrochloride improving learning and memory function in VD would be discussed.Methods: The study is made up of three sections. Section one was to establish VD models, Kunming mice were subjected for continuously three repeated times ischemia-reperfusion through the ligation of the bilateral common carotid arteries, accompanied by sham group and drug group (donepezil hydrochloride); the capabilies of learning and memory of mice were investigated by the stepdown test and water maze test, and the behaviors were observed after mice had been bred for 28 days. In section two, the mice's cerebral tissue were fast taken out, fixed up via perfusion of 4% paraformaldehyde solution, then we respectively observed the pathological change of hippocampus in each group. In section three, the tissue were dyed by immunohistochemistry technique. Then the expressing change of PKC in hippocampus in each group was observed by light microscope, mean optical density (OD) of PKC positive cells were calculated, so that the differrent expression in each group was compared.Results: (1) Step-down test: The abilities to learning and memory in model group decreased evidently that was reflected by the prolongation of response period (P<0.05) and increase of the error times (P<0.05) during the learning phase, and by decrease of latent period (P<0.05) and increase of the error times (P<0.05) during the memory phase. However, the grades of learning and memory in drug group ameliorated apparently, compared with model group (P<0.05), nevertheless, no distinction was detected between drug group and sham group (P>0.05). (2) Water maze test: The notably reduced grades of learning and memory in model group were shown as the prolongation of the whole course time of swimming and increase of the error times during both learning phase (P<0.05) and memory phase (P<0.05), whereas, the grades in drug group improved apparently, compared with model group (P<0.05), similarly, no difference was discovered between drug group and sham group (P>0.05). (3) HE stainning in hippocampus: In sham group, the hippocampal profile was clear, there were 3 to 5 layers pyramidal cells, circinal and big nucleus, clear nucleolus. The pyramidal cells ranged tightly. However, in model group, there were decreased layers pyramidal cells that ranged loosely, their nucleus that had not clear structure, became smaller, were dyed strongly. But above mentioned pathologic changes eased off in drug group. (4) Expressing change as to PKC in hippocampus: In sham group, CA1 area in hippocampus was clearly arranged in light microscope, there were abundant positive neurons, brown and yellow, ranged tightly, rounded or elliptic body, and prominency was observed in some bodies. However, in model group, the number of positive neuron dyed lightly that ranged loosely, was obviously decreased, compared with sham group. In drug group the number of positive neuron dyed deeply that ranged tightly was more than in model group. Through calculating mean optical density of positive neuron, we discovered that in model group, mean optical density of PKC positive neuron was less than in sham group(P<0.05), and their mean optical density in drug group increased compared with model group(P<0.05), no distinction was found between drug group and sham group(P>0.05).Conclusions: (1) The study has successfuly established VD model that imitated the clinical intelligent dysfunction of VD, as it was ascertained by step-down test and water maze test. (2) HE stainning in hippocampus show that pyramidal cells was damaged, in the mean time, the effect of donepezil hydrochloride was demonstrated in the study. (3) It was confirmed that decreased expression of PKC in hippocampus related to cognitive damage in VD, donepezil hydrochloride can enhance learning and memory capacity by inhibiting AchE activity in hippocampus . |
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