胚胎期低剂量甲基汞暴露大鼠的操作行为测试

Operant-Behavior Tests in Rats Prenatally Exposed to Low Level Methylmercury

目的 建立起电脑控制的大鼠操作行为测试系统 ,探讨胚胎期低剂量甲基汞暴露对大鼠学习记忆能力的影响。方法 以氯化甲基汞 0 ,0 .0 1,0 .0 5 ,2 .0 0 mg/ (kg·d)于 Wistar孕鼠妊娠 6～ 9d进行灌胃处理。仔鼠 10周龄时 ,于4个实验组中各随机抽取 8只 ,采用自动化操作行为测试系统于夜间进行 15 h(16∶ 0 0～ 7∶ 0 0 )的行为测试 ,测试程序为高 /低频度差别强化率 ,前者要求大鼠多次重复压杆 ,后者则需要在得到强化物 (45 mg小食丸 )后等待一段时间再压杆。实验采用双盲法。结果 3个剂量组大鼠的学习成绩均比对照组降低 (P<0 .0 5或 P<0 .0 1) ,高频度差别强化率存在剂量 -反应关系 (rs=- 0 .72 73,P<0 .0 1)。结论 胚胎期低剂量甲基汞暴露可影响大鼠神经系统的生长发育 。

Objective To establish the computer controlled operant behavior test system for rats,and to explore the effects of prenatal exposure to low level methylmercury on the ability of learning and memory in rats Methods The Wistar rats were perorally perfused by 0,0.01,0.05,2.00 mg/(kg·d) methylmercury chloride(MMC) during the period from the 6th day to the 9th day after conception respectively.In every dose group,8 offspring aged 10 weeks were randomly selected to be tested by operant behavior test system.The operant performance was measured in automated nocturnal 15 hour session(16∶00~7∶00).The trial pragram Differential Reinforcement of High (DRH) rate and of low (DRL) rate was carried out by a double blind method.The DRH tests required observed animals to press levers frequently,while the DRL test required the subjects to respect a blocking interval after a reinforcement for pressing lever again. Results The performances scores of 3 exposure groups at doses of 0.01,0.05 and 2.00 mg/(kg·d) methylmercury were significantly lower than that of the control group( P<0 05, or P<0 01 ).The significant dose response relationships between the performance scores and the tested levels of methylmercury was observed in DRH test r s= -0 727 3, P<0 01) Conclusion Prenatal exposure to methylmercury at lower dosage affected the growth and development of nerve system of the rat offspring,the learning and memory ability was also damaged