苯并[a]芘暴露对小鼠条件性恐惧记忆的影响

The effects of subacute benzo [a] pyrene exposure on conditional fear memory in mice

目的:研究苯并[a]芘染毒对小鼠条件性恐惧记忆的影响。方法:健康8周龄雄性C57/BL6小鼠随机分为3组:染毒组、溶剂对照组和生理盐水对照组,每组12只。各组分别连续腹腔注射苯并芘(2 mg/kg)、等体积植物油和等体积生理盐水10 d,在染毒结束后第2周和第4周各取6只分别进行条件性恐惧记忆测试和开放旷场测试。结果:条件性恐惧记忆测试结果显示,染毒后第2周和第4周,染毒组小鼠在训练阶段僵立时间百分比与对照组无明显差异;在背景提示阶段染毒组小鼠僵立时间百分比显著低于对照组(P <0. 05);在声音提示阶段染毒组小鼠僵立时间百分比同样显著低于对照组(P <0. 05)。在整个条件性恐惧记忆测试过程中,各组动物僵立时间百分比的变化趋势也存在显著性差异(P <0. 05)。开放旷场测试结果显示,染毒后第2周和第4周,各组动物条件性恐惧记忆刺激前后对比,对照组在中心区域停留的时间占比显著降低(P <0. 05),而染毒组前后对比无显著性差异。结论:苯并[a]芘暴露对小鼠的恐惧记忆水平具有显著的抑制作用,并因此减少恐惧伴随情绪-焦虑的产生。

Objective: To investigate the effect of benzo[a]pyrene on conditional fear memory in mice. Methods:Thirty-six healthy male C57/BL6 mice were randomly divided into 3 groups: the exposed group,the solvent control group and the saline control group,with 12 mouse in each group. They were continuously intraperitoneally injected with benzopyrene( 2 mg/kg),an equal volume of vegetable oil and an equal volume of physiological saline for 10 days,and then continued to be kept. At the 2nd week and the 4th week post injection,6 mice in each group were started to behavioral testing for contextual and cued fear conditioning test and open field test,respectively. Results: The contextual and cued fear conditioning test showed that there was no significant difference between the percentage of freezing time of the mouse in the exposed group and the control group during the training phase;During the contextual phase,the percentage of freezing time of the mouse in the exposed group was significantly lower than that of the control group( P < 0. 05);During the cued phase,the percentage of freezing time of the mouse in the exposed group was also significantly lowerthan that of the control group( P < 0. 05);there was also a significant difference in the change trend of percentage of freezing time in the whole contextual and cued fear conditioning test( P < 0. 05). The open field test showed that the proportion of time spent in the central area was significantly lower in the control group before and after the conditional fear memory stimulation( P < 0. 05),and there was no significant difference in exposed group before and after stimulation. Conclusion: Benzo[a]pyrene exposure has a significant inhibition on fear memory in mouse,and thus reduces fear associated with mood-anxiety.