Abstract: Objective To analyze the correlation of different chronic restrained programs with depressive behavior and learning and memory ability in adolescent mice, in order to discuss the effects of leptin (LP) on depression, learning and memory disorders induced by chronic restrained stress, and its related receptor mechanism. Methods Totally 70 healthy male C57 mice aged 3 to 4 weeks after birth were subjected to low-intensity (2h)/high-intensity (4h) chronic restrained stress for 10 consecutive days. Then the ideal bondage model was chosen. LP was injected intraperitoneally, and the depressive behavior of the mice was observed by open field test (OFT). Morris water maze was used to detect their learning and memory abilities. ELISA was used to determine the expression of serum LP. The expression of NMDAR₁ and GABAR in the hippocampus and medial prefrontal cortex (mPFC) was detected by Western blotting. Results In OFT, the residence time in the central region of HCRS mice was significantly lower than that in control group[HCRS:(95.2±17.3)s, control:(157.1±25.5)s, P<0.01], which in HCRS + saline group was significantly lower than that of sham group[(97.7±25.1)s vs. (148.6±24.8)s, P<0.01]. The central area residence time of HCRS + H-LP group was close to that of sham group. In the navigation experiment of Morris water maze, the escape latency of HCRS mice in four quadrants was lower than that of control group, which had no statistical difference between HCRS+H-LP and sham mice. The average number of station crossings in Morris water maze was lower in HCRS group than that of control group (HCRS: 2.1±0.9, control: 4.2±1.9, P<0.05), and there was no statistical difference between HCRS+H-LP and sham group. Serum LP level in HCRS group (4.2±1.3) was significantly lower than that in control group (10.4±2.9, P<0.01), and there was no statistical difference between the HCRS+H-LP and sham group. The expression level of NMDR₁ in mPFC in HCRS group was significantly lower than that in control group. After high LP injection, the expression level of NMDR₁ was close to normal group. Conclusions High chronic restrained stress can cause mood, learning and memory disorders in adolescent mice. Chronic systemic application of high concentration LP can improve these disorders, which may be related to the decreased expression level of NMDAR₁ in mPFC.

Key words: depression, learning and memory, leptin, chronic restrained stress

摘要： 目的 观察不同慢性束缚方案与青春期小鼠抑郁行为及学习记忆能力的相关性,探讨瘦素对慢性束缚应激造成的情绪障碍和学习记忆的影响及相关受体机制。方法 选取出生后3~4周龄健康雄性C57小鼠70只,连续10d低强度(2h)/高强度(4h)束缚应激,筛选理想的束缚模型,腹腔注射瘦素(LP),矿场实验(OFT)观察小鼠抑郁行为,Morris水迷宫检测小鼠的学习记忆能力,酶联免疫法检测血清LP水平,Western blotting实验检测海马和内侧前额叶皮层(mPFC) N-甲基D-天冬氨酸受体1(NMDAR₁)和γ氨基丁酸受体(GABAR)的表达。结果 OFT实验中,高强度束缚(HCRS)组小鼠的中央区停留时间低于对照组[HCRS组:(95.2±17.3)s,对照组:(157.1±25.5)s,P<0.01]。HCRS+盐水组小鼠的中央区停留时间低于假手术组(分别为97.7±25.1和148.6±24.8;P<0.01),HCRS+高浓度LP(H-LP,0.05mg/kg)组小鼠在中央区停留时间与假手术组小鼠接近。Morris水迷宫定位航行实验中,HCRS小鼠在四个象限的逃避潜伏期均低于对照组,HCRS+H-LP小鼠与假手术小鼠差异无统计学意义。Morris水迷宫空间探索实验的平均穿越站台次数,HCRS小鼠低于对照组(HCRS组:2.1±0.9, 对照组:4.2±1.9;P<0.05),HCRS+H-LP小鼠与sham小鼠差异无统计学意义。血清LP水平检测显示,HCRS组(4.2±1.3)低于对照组(10.4±2.9;P<0.01),HCRS+ H-LP组与假手术组差异无统计学意义。蛋白质印迹法结果显示,HCRS组小鼠的mPFC NMDR₁表达水平低于对照组。应用高浓度LP后NMDR₁表达水平接近正常水平。结论 HCRS可以造成青春期小鼠的情绪和学习记忆障碍,全身慢性应用高浓度LP能够改善HCRS导致的青春期小鼠抑郁样行为和学习记忆障碍,这可能与瘦素抑制mPFC NMDAR₁表达水平降低有关。

关键词: 抑郁, 学习记忆, 瘦素, 慢性束缚应激