不同剂量碘对小鼠迷宫前后大脑乙酰胆碱和乙酰胆碱酯酶的影响

The effect of the cerebrum acetylcholine and acetylcholinesterase in neonatal mice treated with different iodine doses before and after Morris water maze training

目的研究不同剂量碘对迷宫前后小鼠大脑乙酰胆碱(Ach)量、乙酰胆碱酯酶(AchE)活力的影响。方法采用随机区组实验设计方法将昆明初断乳鼠随机分为适碘组(I),不同剂量高碘(Ⅱ￣Ⅴ)组,碘通过饮水给予,喂养100d,复制成高碘动物模型,交配生仔,取25日龄各组仔鼠迷宫训练前12只、迷宫训练后10只测定大脑Ach含量和AchE活力。结果①除Ⅲ组外,其余组逃避潜伏期均随实验次数增加而减少(P<0.05),高碘组部分实验次数逃避潜伏期较适碘组明显延长(P<0.05)。②迷宫前第Ⅳ、Ⅴ组Ach含量较适碘组明显减少(P<0.05);迷宫后第Ⅱ、Ⅲ组较适碘组明显减少(P<0.05);迷宫后与迷宫前比较,除第Ⅱ组外其余组均较迷宫前显著增多(P<0.05)。③迷宫前、迷宫后各组AchE活力虽存在显著差异(P<0.05),但Ⅱ￣Ⅴ组与适碘组比较差异无统计学意义(P>0.05);迷宫前后同组比较差异也无统计学意义(P>0.05)。结论高碘引起的学习记忆功能障碍与脑内合成的Ach数量减少有关;强化训练小鼠学习记忆功能,可引起脑内Ach合成增多,Ach含量改变与AchE活力无明显关联。

Objective To detect the cerebrum acetylcholine （Ach） content and acetylcholinesterase （AchE） activeness of the Kunming 25-day neonatal mice treated with different high iodine doses before and after Morris water maze training. Methods The weaning KM mice were randomly divided into five groups. The high iodine model mice were successfully duplicated by feeding for 100 days with distilled water containing different KIO3 concentrations, i.e. 50（Ⅰ）, 250（ Ⅱ）, 500（ Ⅲ ）, 1 500（Ⅳ ）, and 3 000（ Ⅴ ） mg·L^-1 respectively. The group took 50 mg·L^-1 of proper iodine dose was of control group, and the groups of 250 - 3 000 mg·L^-1 were of high iodine groups. The model mice were mated at a ratio of 1 male to 2 female. The 20-day neonatal mice were trained with the Morris water maze to build them the learning and memory function. The cerebrum acetylcholine content and acetylcholinesterase activity of the KM 25-day neonatal mice were detected. Twelve samples of each group of pre-Morris water maze training and ten samples of each group of after- Morris water maze training were detected. Results ①The escape latency of all groups hut Ⅲ group was significantly decreased with the increase of the experiment times of the mice （P 〈 0.05）. The escape latency of mice in part of the experiment was obviously different among all groups, showing that the escape latency of mice in high iodine groups was longer than that in control group （P 〈 0.05）. ②Before Morris water maze training, the cerebrum Ach concentration in IV and V groups evidently decreased than that in control group （P 〈 0.05）, after Morris water maze training, the Ach concentration in Ⅱ and Ⅲ groups obviously decreased than that in control group （P 〈 0.05 ）. The Ach concentration in all groups hut Ⅱ group of the after-Morris water maze was more than that of pre-Morris water maze （P 〈 0.05 ）. ③The cerebrum AchE activities of the pre- and after- Morris water maze mice were detected that there was an evident difference among all groups, however the AchE activity in Ⅱ -Ⅳ groups was not obviously different from the control group either of pre-Morris water maze or after-Morris water maze. Conclusions High iodine can result in the hindrance of the learning ability and memory of the neonatal mice, which is relevant to the decrease of cerebrum Ach concentration. Intensifying the learning ability and memory function of the mice would enhance the cerebrum Ach content of the mice, which is irrelevant to the change of cerebrum Ache activity.