褪黑素对急性睡眠剥夺大鼠记忆的影响

背景:睡眠剥夺可引起动物或人学习记忆受损,还可引起大鼠脑组织一氧化氮含量升高。褪黑素具有抗自由基、抗氧化作用。有报道褪黑素对氯化铝、吗啡戒断等因素致动物学习记忆损伤有改善作用,但褪黑素是否对睡眠剥夺致动物学习记忆损伤有影响?目的:观察褪黑素对睡眠剥夺大鼠记忆的影响及并分析其可能的作用机制。设计:随机分组对照观察的动物实验。单位:解放军第四军医大学基础部基础医学教学实验中心和护理系。材料:实验于2005-01在解放军第四军医大学基础医学教学实验中心完成。选择成年雄性SpragueDawley大鼠24只,随机数字表法分为3组,对照组、褪黑素小剂量组、褪黑素大剂量组,每组8只。方法:小剂量褪黑素组和大剂量褪黑素组,采用褪黑素剂量分别为5mg/kg和15mg/kg,配制成2mL溶液,每天下午17:00腹腔注射,对照组在相同时间腹腔注射生理盐水2mL。1次/d,连续7d,后给予睡眠剥夺3d。此间依然按分组每日给予褪黑素或生理盐水。采用小平台水环境法建立大鼠睡眠剥夺模型,睡眠剥夺48h和睡眠剥夺72h后用水迷宫测试大鼠的记忆,用逃避潜伏期(s)作为大鼠的学习记忆水平变化的指标,逃避潜伏期时间越短,说明大鼠的空间记忆越好。各组睡眠剥夺结束后大鼠立即处死,于冰浴中取出海马与大脑皮质。用硝酸还原法检测大鼠大脑皮层和海马中一氧化氮含量,用硫代巴比妥法检测丙二醛含量。主要观察指标:睡眠剥夺48h和睡眠剥夺72h后逃避潜伏期测评结果。大鼠大脑皮质和海马中一氧化氮和丙二醛含量。结果:在实验过程中无动物死亡,全部进入结果分析。①各组大鼠睡眠剥夺48h、72h的水迷宫逃避潜伏期差异有显著性意义(F=11.886,P=0.000)和(F=5.440,P=0.012),睡眠剥夺48h、72h小剂量褪黑素组和大剂量褪黑素组的逃避潜伏期均较对照组显著减小,且睡眠剥夺48h大剂量组逃避潜伏期比小剂量组减小。②各组大鼠脑内一氧化氮和丙二醛含量差异都非常显著,大脑皮质一氧化氮(F=14.038,P=0.000)、丙二醛(F=27.414,P=0.000)和海马一氧化氮(F=22.692,P=0.000)、丙二醛(F=14.316,P=0.000)。与对照组比较,两个实验组大鼠大脑皮质和海马一氧化氮和丙二醛含量降低都非常显著,且大剂量组与小剂量组海马一氧化氮含量相比差异也有显著性,呈现出量效关系。结论:褪黑素对睡眠剥夺大鼠记忆障碍有改善作用,这种作用可能与抑制睡眠剥夺大鼠大脑皮质和海马中一氧化氮及丙二醛的升高作用有关。

Effect of melatonin on memory of rats after acute sleep deprivation

BACKGROUND: Sleep deprivation cannot only cause learning and memory impairment of animal and human, but also lead to increased content of nitric oxide in brain tissue of rats. Melatonin has the effects of antifreeradical and antioxidation. It has been reported that melatonin can improve aluminum chloride and morphine abstinence induced learning and memory impairment of animal, however, whether it has influence on sleep deprivation induced learning and memory impairment is not very clear. OBJECTIVE: To observe the effect of melatonin on memory of rats after sleep deprivation and analyze its possible mechanism. DESIGN: Randomized controlled trial.SETTING: Teaching and Experiment Center of Basic Medicine and Department of Nursing, the Fourth Military Medical University.MATERIALS: The experiment was performed in Teaching and Experiment Center of Basic Medicine of the Fourth Military Medical University in January 2005. A total of 24 adult male Sprague Dawley rats were selected and randomly divided into 3 groups, namely, control group, small dosage of melatonin group and large dosage of melatonin group, with 8 in each group on the basis of random digits table.METHODS: To rats in small dosage of melatonin group and large dosage of melatonin group, the dosage of melatonin was 5 mg/kg and 15 mg/kg respectively, which was made into 2 mL solution and intraperitoneally injected into the rats at 17:00 o'clock every day, while rats in control group were injected with 2 mL physiological sodium at the same time, once a day for continuous 7 days. Then a 3-day sleep deprivation was given to the rats; melatonin or physiological sodium were also given according to different groups during these days. Rat model of sleep deprivation was established by "Flower Ppot" technique; water maze was used for detecting the memory of rats after 48-hour and 72-hour sleep deprivation; took escape latency (s) as indicator of changes of learning and memory of rats; the shorter the escape latency, the better the spacial memory of rats. When sleep deprivation was finished, all the rats were put to death and hippocampus and cerebral cortex were taken out in ice bath. The content of nitric oxide in cerebral cortex and hippocampus was detected with the method of nitrate reduction, and malondialdehyde (MDA) with the method of thiobarbital acid.MAIN OUTCOME MEASURES: Results of escape latency after 48hour and 72-hour sleep deprivation. Contents of nitric oxide and MDA in cerebral cortex and hippocampus of rats.There was significant difference in escape latency in water maze after 48-hour and 72-hour sleep deprivation among each group (F=11.886, P=0.000)and (F=5.440, P=0.012); the escape latency after 48-hour and 72-hour sleep deprivation remarkably decreased both in small and large dosage of melatonin groups as compared with control group, and the latency after 48-hour sleep deprivation was shorter in large dosage group than that in small ide and MDA in brain of rats among each group, namely, nitric oxide in cerebral cortex (F=14.038, P=0.000), MDA in cerebral cortex (F=27.414,P=0.000), nitric oxide in hippocampus (F=22.692, P=0.000), MDA in hippocampus (F=14.316, P=0.000). Compared with control group, the contents of nitric oxide and MDA in cerebral cortex and hippocampus in the two experimental groups decreased significantly, and there was obvious difference in the content of nitric oxide in hippocampus between large and small dosage groups, which showed a dose-effect relationship.CONCLUSION: Melatonin can improve memory impairment of rats after sleep deprivation, which may be closely related to the effect of inhibiting the increase of nitric oxide and MDA in their cerebral cortex and hippocampus.