铅暴露对大鼠脑海马mGluR5表达和学习记忆影响

Effect of lead exposure on protein expression of mGluR5 in hippocampus and learning memory in rats

目的观察发育期慢性低浓度铅暴露对大鼠脑海马代谢型谷氨酸受体5(mGluR5)表达和学习记忆能力影响。方法 30只孕鼠按体重随机分成3组,分别给予双蒸水、0.05%、0.20%醋酸铅饮水,断乳后仔鼠自行饮用含铅水,至出生后28、56 d用水迷宫方法测试仔鼠学习记忆行为改变;蛋白印迹(Western blot)方法检测脑海马mGluR5蛋白表达。结果发育期慢性低浓度铅暴露可导致仔鼠空间定位航行能力降低;与对照组比较,训练第3、5、7 d,0.05%、0.20%醋酸铅组大鼠寻找平台时间[分别为(40.13±9.20)、(32.82±6.45)、(26.83±7.12)和(61.50±13.84)、(54.51±9.65)、(19.81±4.92)s]明显延长,差异有统计学意义(P<0.05);生后第7、14、21、28 d,0.05%,0.20%醋酸铅组脑海马mGluR5蛋白表达量分别为[(0.607±0.027)、(0.845±0.010)、(0.713±0.004)、(0.587±0.011)]和[(0.540±0.025)、(0.573±0.014)、(0.551±0.014)、(0.492±0.017)],均明显低于对照组(P<0.05)。结论孕鼠低水平铅暴露可致仔鼠空间学习能力降低,其机制可能与脑海马mGluR5蛋白表达水平下降有关。

Objective To observe effects of low level lead exposure during pregnant on expression of metabotropic glutamate receptor 5（mGluR5）in hippocampus and learning and memory in rats.Methods Thirty pregnant rats were randomly divided into 3 groups,and the rats were fed with doubly distilled water in control group and 0.05%,0.2%lead acetate（PbAc）solution in treatment groups via drinking water during pregnancy and lactation.After weaning,the offspring rats were directly fed with drinking water as their dams.Western blot was used to detect the protein expression of mGluR5 in hippocampus of offspring rats at postnatal 7,14,21,and 28 days,respectively.The contents of lead in blood and hippocampus were determined with atomic absorption spectrophotometer at postnatal 28 days.Morris water maze test was used to observe the change of learning and memory at postnatal 56 days.Results Low level lead exposure during pregnancy resulted in the decreases of spatial positioning navigation in the offspring rats.The time of searching for the platform in the offsprings of the rats in 0.05%and 0.2%PbAc groups were 40.13±9.20,32.82±6.45,26.83±7.12 and 61.50±13.84,54.51±9.65,19.81±4.92 seconds at 3,5,and 7 day of training,compared to those of the control group,which exhibited a significant extension（P〈0.05）.The expression of mGluR5 in hippocampus of 0.05% and 0.2% PbAc group at postnatal 7,14,21,and 28 days were 0.607±0.027,0.845±0.010,0.713±0.004,and 0.587±0.011 and 0.540±0.025,0.573±0.014,0.551±0.014 and,0.492±0.017,with a decreased tendency compared to those of the control group（P〈0.05）.Conclusion Chronic lead exposure results in decrease of spatial learning and memory and its effect may relate to the decline of expression of mGluR5 in hippocampus in rats.