发育期邻苯二甲酸二（2-乙基己基）酯暴露对小鼠学习记忆的影响

Effects of developmental exposure to DEHP on learning and memory of mice

目的 观察小鼠发育期暴露邻苯二甲酸二（2-乙基己基）酯（DEHP）对其学习记忆能力的影响.方法 取自然分娩SPF级ICR小鼠,共14窝,每窝于出生后4d调整为5只雄鼠,同窝仔鼠随机分为空白对照组、溶剂对照组以及DEHP处理组[10、50、200 mg/（kg· d）],每组14只.出生后5d开始按体重进行灌胃给药,每日1次,至出生后38 d,期间称量并记录小鼠体重.出生后26 d进行旷场实验,评估小鼠自发性探索活性及焦虑状态;出生后30 d开始进行Morris水迷宫实验,评估小鼠空间学习与记忆能力.行为学实验结束48 h后处死小鼠,分离双侧大脑海马组织,应用蛋白免疫印迹法检测突触后致密蛋白95（PSD95）与突触素Ⅰ（synapsin Ⅰ）蛋白表达水平.结果 与溶剂对照组比较,200 mg/（kg·d）DEHP组小鼠体重降低,旷场中央区运动时间明显减少,Morris水迷宫实验中登台潜伏期延长,差异均有统计学意义（P＜0.05）.与溶剂对照组比较,50 mg/（kg·d） DEHP组小鼠体重增长和情绪行为均未发生明显改变,差异均无统计学意义（P＞0.05）,而Morris水迷宫中目标象限运动距离及时间明显减少,差异有统计学意义（P＜0.05）;与溶剂对照组比较,各剂量DEHP组小鼠海马PSD95蛋白表达水平降低,200 mg/（kg·d）DEHP组小鼠海马synapsin Ⅰ蛋白表达水平降低,差异有统计学意义（P＜0.05）.结论 发育期暴露DEHP,在不明显影响一般发育、不引起焦虑情绪的剂量下,可损害小鼠海马突触发育,降低空间记忆能力.

Objective To investigate the effects of developmental exposure to DEHP on learning and memory of mice.Methods Male littermates of ICR mice randomly assigned to five experimental groups （n=14 for each condition） on PND4 to receive distilled water,vehicle and 10,50 and 200 mg/（kg·d） DEHP from PND5 to PND38 by gavage,weighing and recording body weight of mice.Open field task were conducted on PND 26 and Morris water maze task were begun from PND30 to PND 37 to evaluate spontaneous exploration activity and emotion,spatial learning and memory performance of pubertal mice,respectively.On PND39,all animals were killed and hippocampi were isolated on ice,then total proteins of hippocampus were extracted,followed by determining the expression of PSD95 and synapsin Ⅰ by western blotting.Results 200 mg/（kg· d） DEHP significantly reduced the growth of body weight of mice and the time staying in the central area in open field,prolonged the time searching the hidden platform in Morris water maze （P〈0.05）.50 mg/（kg· d） DEHP didn＇t change the growth of body weight and the emotion （P〉0.05）,but reduced the percent of time and distance in the target quadrant during the probe trial of mice in Morris water maze （P〈0.05）.The results of western blotting showed that DEHP significantly reduced the expression of PSD95 in hippocampus of mice with all dose groups（P〈0.01）,but only 200 mg/（kg ·d） DEHP reduced the expression of synapsin Ⅰ （P〈0.05）.Conclusion Developmental exposure to DEHP can damage the development of synapse in hippocampus,adversely impacting spatial memory performance of mice at a dose that are insufficient to significantly influence the general development and result in anxiety.