The Relation Between Memory Of Pseudo-VD Model Rats And NMDA And AMPA Subunite, Neuronalion Channels And Intervention Of Ginsenoside Rg₂

Aim To investigate the relation between learning and memory and the gene expression of N-methy-D-aspartate, a-amino-3-hydroxy-5-mehtylisoxazole-4-propionic acid subunit, including NR1,NR2A,NR2B and GluR2 ,and intervention of ginsenoside Rg₂ in vascular dementia model rats with chronic cerebral hypoperfusion, besides,to explore the effects of ginsenoside Rg₂ on neuronal sodium, calcium and potassium channels and the effective mechanism of ginsenoside Rg₂ on learning and memory in the rats. Excitatory amino acids play a determinate role on pathogenesy of vascular dementia, glumatic acid can especially take a important role , because glumatic acid as well as it's receptor participate development and elongation of synapse, and synaptic plasticity participate many mechanism of learning and memory process,and neurotoxicity of glumatic acid produced a markedly effect by it's receptor, therefore it has important significance to approach the relation between abnormality of GluR and morbility of dementia.Vascular dementia is a common chronic and progressive disease in clinic, which concerned with ischemical cerebropathia. permeability dysfunction of natrium , potassium and calcium ion channel and disorder of ionic balance of exterior and interior neurocyte are one of important mechanisms in ischemic brain injure after cerebral ischemia. Disequilibrium of ion homeostasis happen in commitment of brain ischemia ,and induce succedent a series of cascade reaction, finally result in abnormity of intelligence and behavior in patients with VD .The pathogenesis of the disease is complicated and not yet elucidated at present, and so far is not good active drug to treat VD, therefore ,meanwile explored the pathogenesis of VD, we observed intervention of ginsenoside Rg₂ and analysed it's possible way of neuroprotective effect.Methods (1)Vascular dementia model rats was induced by permanent occlusion of bilateral common carotid arteries(2-VO). (2) Evaluation criterion and test method of animal model After operation 1 day , the rats model was evaluated by index of brain apoplexy and neurological symptom. (3) Open filed method to test exploratory response and spontaneous movement of the model rats,different dosage of ginsenoside Rg₂ was given 1 day after operation, contrasting with nimodipine. To measure the activity of vascular dementia model rats in fifth day by open field. (4) Water maze test praxiology spatial learn and memory ability was observed before operation and sixth day and seventh day after operation by delayed nonmatching-to-position task(DNMPT) in the water maze, respectively. (5)The mRNA expression of NMDAR1,NR2A, NR2B and GluR2 were determined by RT-PCR and normalized byβ-actin as internal standard. Each gene expression level was quantified by the intensity ratio of an internal control bandβ-actin to target one. (6)The effects of ginsenoside Rg2 on sodium, calcium and potassium channels in cultured hippocampal neurons were observed by using whole-cell recording technique.Results (1)Verifying the animal model with VD behavior character to be successful by evaluating the shock index and neurological symptoms. (2)It is showed by open field tests that vertical movement and level movements were reduced in the model rats, the difference is significant compared with sham operation group (p＜0.01). (3)Water maze tests indicated that learning and memory ability is obviously lowered in VD model rats, showing that the time for model rats to swim of information (IS) and choice (CS) was eulonged and the correct rate was declined, the difference was significan (p＜0.01) compared with the control group and sham operation group. (4)Ginsenoside Rg₂ 2.5,5,10mg/kg shorten the time of IS sand CS in a dose-dependent manner in the rats,the difference is significant compared with the model group (P＜0.01),but nimodipine hasn't obviously shortened the time. (5) Accordingβ-actin as internal standard RT-PCR method analysis showed that expression of NR1 mRNA was enhanced and experssion of NR2A,NR2B,GIuR2 were attenuated in model group compared with the control group; expression of NR1 mRNA was attenuated and expression of NR2A,NR2B,GluR2 were increased in the groups treated by ginsenoside Rg₂ compared with the model group, there were no obviously changes in the group treated by nimodipine. (6)The experimental results of patch-clamp indicated that ginsenoside Rg₂ had no significant effect on Na⁺, K⁺,Ca²⁺ ion channel in the cultured hippocampus ceils with no-anoxia condition.Conclusions (1)The learning and memory ability, exploring ability and spanteneous movement were declined in imitated vascular dementia model rats with chronic cerebral hypoperfusion, and the expression of mRNA of NMDAR1 was increased and the experission of mRNA of NR2A,NR2B and GluR2 decreased. (2) Through regulating NMDAR1,NR2A,NR2B and GluR2 gene expression and reduing the toxicity of excitatory amino acids ginsenoside Rg₂ significantly improve the space learning and memory ability and behavior disorder of the rats with imitated VD induced by permanent bilateral common carotid artery ligation.(3) Ginsenoside Rg₂ had no effect on sodium, calcium and potassium channels in normal cerebral neuronal, which demonstrated ginsenoside Rg₂ protected neurons through other ways under normal conditions.Postgraduate student: Li Zhang (Physiology)Directed by Prof. Yi Jin...