叶酸缺乏的离乳大鼠学习记忆能力与海马突触体膜流动性改变的相关性研究

STUDY ON RELATIONSHIP BETWEEN THE FOLATE DEFICIENCY ON WEANLING RAT'S LEAREVG AND MEMORY AND THE HIPPOCAMPAL SYRNAPTOSOMAL MEMBRANE FLUIDITY

初步探索叶酸缺乏的离乳大鼠学习记忆能力的改变与海马突触体膜流动性之间的关系,从膜功能的角度为叶酸缺乏影响学习记忆能力提供动物学方面的依据。对５４只刚离乳的健康雄性ＳＤ大鼠,随机分成实验组(ＦＤ)、对饲组(ＰＦ)和对照组(ＡＬ)三组。实验组饲以去叶酸的ＲＨＡＡ配方饲料,另二组饲以添加了８ｍｇ叶酸/ｋｇ膳食的ＲＨＡＡ饲料,对饲组按实验组的进食量加以控制,对照组不控制进食。每周记录体重和摄食量两次。分别于饲养第２和第６周末测定血清叶酸浓度和进行Ｍｏｒｒｉｓ水迷宫测试大鼠的学习记忆能力,记录平均逃避潜伏期和分析原平台象限游泳距离占游泳总距离的百分比;分离海马突触体,透射电镜作形态学证实,用荧光物质ＤＰＨ标记突触体后测定荧光强度,后者反映突触体膜流动性。对血清叶酸浓度、平均逃避潜伏期及原平台象限游泳距离百分比、膜流动性作相关分析。结果显示:实验第２周除实验组血清叶酸浓度降低外(Ｐ＜０．０１),其余各指标在三组间无明显差异(Ｐ＞０．０５);实验组(ＦＤ)从第３周、对饲组(ＰＦ)从第４周开始摄食量减少,生长速度减慢(Ｐ＜０．０５)。第６周实验组(ＦＤ)的平均体重、血清叶酸浓度明显低于对照组(ＡＬ)和对饲组(ＰＦ)(Ｐ＜０．０１),平均逃避潜伏期明显延长。

The relationship of hippocampal synaptosomal membrane fluidity and the alteration of the folate dericiency on weanling rats' learning and memory was preliminarily studied. Our research was expected to provide some zoological evidence to this effect on the aspect of membrane function. 54 male weanling Sprague -Dawley rats were divided into three groups . The folate deficient group received an amino acid - defined diet(RHAA) , the ad libitum control group had the same diet supplemented with folate of 8mg per kg diet, and the pair- fed control group received the folate supplemented diet, but was individually pair- fed to the mean daily food consumption of the folate deficient group. Body weight and food intake were measured twice weekly. At the end of the second and sixth week of the experiment, 27 rats, 9 from each group , were undergone a Morris Water Maze behavioral training for 5 days, an auto - video system recorded the escape latency and the swimming pattern. The serum folate concentration and the fluorescence intensity of the hippocampal synaptosomal membrane(r value) marked by a fluorescent substance DPH, which reflected the membrane fluidity, were also assayed. Correlation analysis was processed among serum folate concentration and fluorescence intensity and the percentage of swimming distance in the platform quadrant. Resulto showed that growth retardation and impaired food intake associated with FD could not be demonstrated in the FD group rats until the end of the 3rd week ( P < 0.05) , while the pair - fed group gradually showed this retardation at the end of the 4th week. At the end of the experiment the FD rats had weight loss, leaving the pair- fed group slightly affected (compared with ad libitum control group, P < 0.05). Decreased serum folate occurred at the end of the 2nd week of the experiment, without alterationof the other parameters. At the end of the 6th week, FD group rats had very low body weight and serum folate concentration ( P < 0.01), with the mean escape latency lengthened and the percentage of swimming distance in the platform quadrant decreased. The fluorescence intensity of the hippocampal synaptosomal membrane increased, which implied reduced membrane fluidity (P <0.0l). Correlation analysis results showed that the fluorescence intensity of the hippocampal synaptosomal membrane(r value)and the serum folate concentration , mean escape latency and the percentage of swimming distance in the platform quadrant were highly correlated( r = -0.527, P<0.05; r= -0.451, P<0.05; r= -0.579, P< 0.05). In conclusion: 1. Folate deficiency could impair the learning and memory of weanling rats and it could reduce weanling rats' hippocampal synaptosomal membrane fluidity. Trie impairment was rather obvious at the 6th week. 2. The reduction of hippocampal synaptosomal membrane fluidity is possibly one of the mechanism of folate deficiency impairing the weanling rats' learning and memory.