| Objective: Mild cognitive impairment(MCI) is a clinical state which is between normal ageing and dementia. MCI is a common neurological degenerative diseases usually occurs in the elderly population, which is a major risk factor for Alzheimer’s disease.TCM theory considers that "Most blockhead is because of sputum", "Want to cure blockhead must to cure phlegm ". Combining the previous research results, we speculate that toxic effects of β-amyloid protein and abnormal expression of NMDA receptor mediated mechanism of synaptic plasticity in MCI are important pathogenic factors, that maybe closely related to TCM phlegm. In this assay, we select 13 months old rats injected with D-galactose subcutaneously, and fed with half high fat diet to establish senile MCI rats model. We study from the following aspects: the behavioral science, neuropathology, Aβ and secretion, NMDA receptor and etc, to observe the effect and mechanism of Ditan decoction in MCI.Methods: Sixty 13 months old rats were randomly divided into blank group, model group, Donepezil group, the high dose Ditan decoction group, and low dose Ditan decoction group, plus 12three months old rats as young control group. The senile MCI rats model were established by subcutaneously injected 50 mg?kg-1 D-galactose for 8 weeks and fed with semi- high-fat diet for 4 weeks in rats of model group, Donepezil group, the high dose Ditan decoction group, and low dose Ditan decoction group. The dosage of low, high dose Ditan decoction group are 4.275 and 8.55g·kg-1, dosage of western medicine group is donepezil 0.9mg·kg-1. The blank group, model group, and young group are giving distilled water. Rats are fed by 10 m L·kg-1 once a day until the end of 8th week. Morris water maze, shuttle box test were used to evaluate model rats’ learning and memory ability. Chemical colorimetry were used to detect serum and cortex levels of rats,SOD, MDA in rats.Light microscopy and transmission electron microscope were used to observe hippocampus morphology. ELISA method was used to detect the level of Aβ1-42 in hippocampus.Levels of PS-1 and PS-2 in hippocampus was detected by immunohistochemistry. Chemical colorimetry to detect the content of neurotransmitter( Ach, Glu) in rat hippocampus and cortex. ELISA method was used to detect the contents of nerve growth factor(NGF,BDNF). Immunohistochemical method was used to observe the rats’ hippocampal NR2 A and NR2 B expression, and realtime RT-pcr was used to detection of NR2 A and NR2 B m RNA expression.Results:1. Compared to young and blank group, escape latency, space exploration experiment times through platform, the target quadrant time of the Morris water maze test had significant difference(P<0.05),and shocked times also increased significantly(P<0.05), initiatial escape latency weresignificantly prolonged of model group rats(P<0.01)the in Shuttle box experiment.Compared with model group, the escape latency were significantly shorten(P<0.05), and shocked times were increased(P<0.05).In aspect of antioxidant ability, the contents of SOD of serum and cortex were significantly increased(P<0.05), and the MDA level were significantly decreased(P<0.05) in Ditan decoction group(high dose and low dose).2. The influence of the rat hippocampus HE dyeing results were compared:(1)The OM results: the model group rats pyramidal cells were distributed and structure damaged in hippocampal CA1 area,and count of normal cells decreased significantly. Compared with model group, the normal pyramidal cells increased obviously in Ditan decoction group(both high dose and low dose):(2) The TEM results: compared with young group, mean diameter of myelinated nerve fiber increased, and the thickness of myelin sheath thickened obviously in the model group; Compared with the blank group, the synaptic cleft structure is not clear, and presynaptic mitochondria cristae is vague.Compared with model group, Ditan decoction group(high dose and low dose) mitochondrial structure roughly normal, synaptic cleft structure is clear, the density of the postsynaptic membrane material thicker.3. Compared with normal group, the content of Aβ1-42 on model group rats in hippocampus increased significantly(P<0.01), and the expressions of PS-1 and PS-2 in hippocampus also increased(P<0.05).Compared with model group, the escape latency of Ditan decoction group(high dose and low dose) were significantly shorten(P<0.05). The content of Aβ1-42 inhippocampus on both high and low dose group decreased(P<0.05). The expressions of PS-1 and PS-2 in hippocampus on both high and low dose group decreased significantly(P< 0.01).4. Compared to young group, the rats’ hippocampus and cortex Ach contents were significantly decreased(P<0.05), Glu contents were significantly increased(P<0.05) in the model group, and the contents of NGFβ, BDNF in hippocampus were significantly decreased(P<0.05). Compared with model group, contents of rat hippocampus and cortex Ach were significantly increased in high dose Ditan and westernmedicine group(P<0.01), Glu content of hippocampus and cortex decreased significantly in high dose Ditan group(P <0.01),and also decreased in the western medicine and low dose Ditan groep(P<0.05). The contents of the western medicine group, Ditan low rat in high dose Ditan group significantly increased(P<0.01).5. Compared to the young and blank group, NR2A、NR2B expression in model group rats hippocampus decreased significantly(P< 0.05), and m RNA gene expression of NR2A、NR2B obviously reduced(P<0.05). High dose Ditan, low dose Ditan group, and western medicine group NR2 A and NR2 B expression in the rat hippocampus were increased compared with model group(P<0.01), and m RNA gene expression of NR2A、NR2B obviously up-regulated(P<0.05); Compared with the westernmedcine group, m RNA gene expression of NR2A、NR2B in high dose Ditan group obviously up-regulated(P<0.05).Conclusion:1. The model rats’ learning and memory ability and spatial orientation ability were decreased significantly, antioxidant capacity were decreased, and pathology in the hippocampus wassimilar to those of natural aging rats. That means it is the ideal model of senile mild cognitive impairment.2. Improving the body(cortex and serum) antioxidant ability, and reversing synaptic structural damage of hippocampal CA1 area, which might be the protect mechanism of Ditan decoction to senile MCI model rats.3. Ditan decoction can adjust the levels of Ach, Glu content in hippocampus and cortex of rats, and increase the hippocampus of rats model NGF, BDNF protein expression to promote the growth of new neurons and synapses and differentiation, and increase the synaptic transmission.4. Reducing γ-secretase(PS1,PS2) protein expression is the key role of reducing Aβ1- 42, so as to improve the level of neuron surface NMDA receptor subunits, and synaptic function was protected. It may be the important mechanism of Ditan decoction improve the synaptic plasticity in senile MCI model... |
PDF Full Text Request