|其他题名||The development of depression models in tree shrews and the evaluation of predict validity by antidepressants|
|关键词||树鼩 抑郁反应模型 预测效度 氟西汀 卡贝缩宫素|
本研究拟以树鼩为模式动物，通过梯度性增强不可控不可逃避电击刺激应激强度（2，4，7天）和丰富应激输入类型来构建新型抑郁反应模型。考察的主要抑郁样行为指标如下：表征习得性无助的逃避失败次数和逃避潜伏期；表征动机缺乏的主动觅食糖水断点；表征快感缺失的糖水偏爱水平及表征社交回避的社交区域停留时间。同时，本研究重点考察了选择性 5-HT 重摄取抑制剂氟西汀（fluoxetine，15 mg/kg）和催产素激动剂卡贝缩宫素（carbetocin，6.4 mg/kg，20 mg/kg）两种药物对上述抑郁样行为的疗效。此外，根据标准化后的症状总分分析了不同药物对抑郁总体状况的影响。主要结果如下：
1， 随着应激强度的梯度性增强，当应激天数达到 4天时，树鼩表现出习得性无助，且可维持2周；而当应激天数增加到7天时，除了习得性无助外，树鼩表现出动机缺乏行为，但行为难以维持2周。提示习得性无助行为是抑郁症发生发展的早期症状，行为表现较稳定，可用于抑郁的初步诊断与筛查；动机缺乏行为是抑郁症发展过程中逐渐出现的行为，行为不稳定，不易于发现及诊治。
2， 经历7天应激的树鼩所表现出的习得性无助被 2周氟西汀给药完全逆转，表明7天应激所构建的抑郁反应模型具有较好预测效度。
3， 为了增加应激后树鼩行为输出类型，我们在7 天应激的基础上增加了慢性温和应激以丰富应激输入类型。结果显示，丰富应激输入类型后，树鼩表现出除习得性无助外的快感缺失和社交回避行为。结果提示，与单一应激刺激相比，综合应激刺激会诱发更多的抑郁样行为，快感缺失及社交退缩可能发生在抑郁症较晚时期，可用于抑郁症疾病发展状况考察。
4， 随着给药时间的增长，当给药一周时，氟西汀和高、低剂量卡贝缩宫素处理均减少了树鼩的逃避失败次数；给药两周后，氟西汀组树鼩的习得性无助被完全逆转而快感缺失和社交回避被部分逆转；与氟西汀组相似，高剂量卡贝缩宫素组树鼩的习得性无助行为也被成功逆转且快感缺失被部分逆转， 但社交回避行为未表现出逆转趋势；而低剂量卡贝缩宫素组仅表现出逃避失败次数的减少。给药期间体重的变化显示，氟西汀慢性治疗导致了体重下降，而卡贝缩宫素对体重没有影响。结果提示药物的疗效随时间而变化，氟西汀和高、低剂量卡贝缩宫素均具有一定的疗效；氟西汀和高剂量卡贝缩宫素给药起效早，药效好于低剂量卡贝缩宫素；卡贝缩宫素给药负作用小于氟西汀。
|其他摘要||Animal models are important tools for the screening of antidepressants and the exploration of mechanisms of depression. However, there are some limitations in the commonly used rodents’ model. Rats and mice are remote affinity to human and their behaviors are relatively simple. It’s difficult to mimic the depression-like behaviors induced by psychological stressors. Moreover, commonly used depression models are usually based on a single behavior or antidepressant, which makes it difficult to explore the heterogeneous in depression syndromes and the specificity in responses to antidepressants. Therefore it’s crucial to develop an effective depression models with various symptoms in a kind of animals that is more affinitive with human. |
Tree shrews are the closest relative of primates. There are congenital superiorities for tree shrews to develop depression models. Firstly, tree shrews are sensitive to stress, especially the social psychological stresses elicited by social defeats for territory. Then, their genes for major stress-regulating receptor proteins,such as the glucocorticoid and the mineralocorticoid receptor, revealed high homologies to the equivalent human genes. Also, instead of corticosterone in rodents, tree shrew has cortisol that activates glucocorticoid receptor, which is identity to human.
In our study, tree shrews were used to develop a new depression model with different stress intensities (uncontrollable and inescapable foot-shocks, 2 days, 4 days and 7 days) and the abundant type of stress. There were four depression-like behaviors: learned helplessness represented by the frequency of failure escape and the escape latency, amotiation represented by the breakpoints of self-administration of sucrose, anhedonia represented by the sucrose preference, and social withdrawal represented by the time spent in the social interaction zone. In addition, two antidepressants, fluoxetine (one of selective serotonin reuptake inhibitors, 15 mg/kg), and carbetocin (an agonist of oxytocin receptors, 6.4 mg/kg, 20 mg/kg), were administrated after stress for two weeks to investigate their curative effects on the behaviors above, as well as the total scores of depressive behaviors. Main results are listed as followed:
1, Learned helplessness (escape failure) displayed and persisted for 2 weeks in tree shrews exposed to 4 days of uncontrollable and inescapable stresses; amotiation appeared accompany with learned helplessness when the total stress extended to 7 days. However, amotiation did not persist for 2 weeks. All the results above suggest that learned helplessness appears after intensive stress experience, so helplessness might be more useful for the preliminary screening and diagnosis.
2, Learned helplessness was completely reversed after the two weeks’ fluoxetine treatments in tree shrews exposed to 7 days’ stresses. It’s suggested that the new depression model maintain a good predictive validity. 3, A series of chronic mild stresses were added to 7 days’ stresses to increase more depression-like behaviors. Two of depression-like behaviors appeared besides learned helplessness, which were anhedonia and social withdraws. It suggests that more depression-like behaviors may appear in tree shrews exposed to more types of stresses. It also suggests that amotiation and social withdrawal may appear at the later stage of depression, so it can represent the development of depression.
4, The frequency of failure escape was reduced in all the three groups (Flu 15, Car 6.4 and Car 20) after one week’s drug treatments. When the treatments were extended to two weeks, learned helplessness was totally reversed while anhedonia and social withdrawal were partially cured in tree shrews in Flu 15; carbetocin at 20 mg/kg had shown the same effect，while the social withdrawal was kept unchanged; carbetocin at 6.4 mg/kg could only reduce the frequency of failure escape. The results also had shown that weights of tree shrews in Flu15 decreased accompanied by time,while those in the carbetocin groups did not. All the data above suggest that there are curative effects in all the groups treated with antidepressants, In addition, the onset of antidepressant action of fluoxetine and high dose of carbetocin is faster than low dose of carbetocin, and more depression-like behaviors were reversed. Also, side effects were fewer in tree shrews treated with carbetocin than fluoxetine.
5, To mimic clinical diagnosis of depression in human, a total scores of depression-like behaviors were calculated as the sum of grade according to standard z-scores of different kinds of behavior tests. The total scores of tree shrews in Flu 15 and Car 20 were significant decreased, while those in saline and Car 6.4 were not. It suggests that fluoxetine and carbetocin (20 mg/kg) have better antidepressant effects. The present study for the first time developed depression models in tree shrews by combining the gradient stress intensities and the enriched stress types. Four depression-like behaviors were elicited, and differences in the curative effects of fluoxetine and carbetocin were reported. This study provided the experimental evidence for the individual-based treatment of depression in clinical.
|孟肖路. 树鼩抑郁反应模型的构建及其抗抑郁药物预测效度的评价[D]. 北京. 中国科学院研究生院,2014.|
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