| Learning and memory are the advanced functions and the advanced neuro-physiological activities of the brain, and also the key elements of intelligence. Mental retardation is a common clinical symptom of the elderly, a major sign of aging, but also one of early and major clinical symptoms in AD patients. Along with the aging of population, the proportion of AD patients is getting increased. The problem of learning and memory impairment thus occurred become increasingly prominent, unfortunately, nowadays there is still lack of the effective treatment method.Longan (Dimocarpus longan lour) is the fruit variety of the second-largest production in Guangxi. Arillus Longan has the multiple physiological functions of anti-stress, anti-oxidation, anti-aging, enhancing immunity, anti-tumor, antibacteria etc. Furthermore, it is also the traditional Chinese medicine for intelligence-improvement. In this experiment, the dried Arillus Longan produced in Guangxi Daxin Shek Kip is used as the experimental drug. Aqueous Extract from Arillus Longan (ALEA) and 95% Ethanol Extract from Arillus Longan (ALEE) were prepared, then their effects on the learning and memory abilities in scopolamine-induced dementia model and their possible mechanism were studied. The main results were following:1 The extraction of ALE and its acute toxicity study in miceALEA and ALEE were extracted by ultrasonic extraction technology, the collection percent of ethanol was about 98% during extracting ALEE. The median lethal dose (LD50) and the maximum tolerated dose (MTD) of ALE could not be measured by pre-test, so the maximum capacity (MLD) was administered to evaluate the acute toxicity of ALE. As the result, the MLD for i.g. in a day of ALEA and ALEE in mice was 117g crude drug / kg and 135g crude drug / kg respectively, equivalent to 117 times and 135 times that of the maximum daily dose of 60 kg-body weight person respectively. At this dosage, no serious toxic reactions and significant visceral organ lesions could be found. It showed that Arillus Longan had no significant toxicity.2 Effects of ALE on the learning and memory abilities and free radical metabolism in scopolamine-induced dementia rats.ALEA and ALEE were respectively given to rats by i.g. for 21 days continually. Day 16 thought day 21, 3mg·kg-1 scopolamine was given by i.p. to establish the dementia model with memory acquisition impairment. The learning and memory abilities were tested by Morris water maze. After the Morris water maze test, the enzyme activities of SOD, GSH-Px and the content of MDA in serum, hippocampus and cerebral cortex were detected by spectrophotometry. Compared with the model group, the escape latency and the first time for crossing platform of ALE groups were significantly decreased, the swimming time and distance in the first quadrant and the frequency of crossing platform were much more increased. And the activities of SOD, GSH-Px were increased significantly, otherwise the activities of TchE and the content of MDA in serum, hippocampus and cerebral cortex were decreased significantly in ALE groups. It showed that ALE could significantly improve the learning and memory abilities in scopolamine-induced dementia rats. This effect may be related to increase the antioxidant activity, scavenge effectively excess free radical for intelligent–improvement goal in scopolamine-induced dementia rats.3 Effects of ALE on the level of cholinergic transmitter in scopolamine-induced dementia rats'hippocampusThe activities of TchE in rats'hippocampus were investigated by spectrophotometry, and the expressions of ChAT in rats'hippocampus were detected by 2-step immunohistochemistry staining. Compared with model group, the expressions of ChAT were increased significantly, and the activities of TchE were decreased significantly in the ALE groups. It suggested that ALE could increase the content of ACh in rats'hippocampus for intelligent–improvement goal in scopolamine-induced dementia rats.4 Effects of ALE on the level of GFAP in hippocampus of scopolamine-induced dementia ratsThe expressions of ChAT in rats'hippocampus were detected by 2-step immunohistochemistry staining. Compared with model group, the expressions of GFAP were decreased significantly. It showed that ALE could reduce the over-expression of GFAP in rats'hippocampus in scopolamine-induced dementia rats.In summary, the present results suggested that ALE was effective in improving the learning and memory impairment in scopolamine-induced dementia rats. As the possible mechanisms, ALE could scavenge free radicals, reduce the degradation of ACh, promote the synthesis of ACh and effectively inhibit the over-expression of GFAP.
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