伏隔核中型多棘神经元兴奋性及海马长时程增强在抑郁症发病中的作用

发布时间：2018-09-13 11:37

【摘要】：抑郁症是现今世界上最流行的精神疾病，在中国有超过2600万人患有抑郁症，具有高发病率及低诊断率的特点，对当今社会带来了严重的影响。同时，抑郁症的产生原因复杂，遗传和环境因素兼而有之，而且在病理上不易显现出可检测的实质性病变特征，因此对人们研究抑郁症的发病机制造成了极大的困扰，直接影响到抗抑郁药物的开发。因此阐明抑郁症的发病机制，为抑郁症的临床治疗提供有效的思路与方法是当今中国乃至世界精神疾病研究领域亟待解决的科学问题之一。近年来负责奖赏及成瘾机制的重要脑区——伏隔核（Nuclear accumbens, NAc）在抑郁发病和抗抑郁药物治疗中的作用受到越来越多的关注。NAc是基底核区域的一个信息整合核团，主要接受来自中脑腹侧背盖区（ventraltegmental area, VTA）的多巴胺能神经投射，参与与情绪调节相关的神经环路。同时，抑郁症发病假说之一的单胺类假说认为多巴胺在抑郁症发病及抗抑郁治疗中有着不可忽视的作用，但是多巴胺对脑内相关脑区神经活动的影响仍不明了，因此如果能够从电生理学的角度，对NAc的神经元放电特点进行研究，并结合行为学和生化学的研究，则能够帮助我们更加全面深入的了解脑内多巴胺系统中的NAc神经元活性在抑郁症的发病过程中的作用及变化情况。另外，我们也对来自于郭熙志教授实验室的一种干细胞因子（stem cell factor, SCF）及其酪氨酸激酶受体c-Kit通路功能受损的基因突变小鼠进行了电生理学的研究。这种基因突变小鼠具有显著的抑郁样行为表现，并且伴随着学习与记忆功能的缺陷和海马区域的神经元再生障碍。因此通过对其海马区突触可塑性的研究，能够帮助我们了解这种基因突变对海马的突触传递及其可塑性的影响，从电生理学的角度解释这种抑郁小鼠在学习与记忆方面出现缺陷的原因。在本研究中，我们选取了两种抑郁症模型鼠Wistar Kyoto (WKY)大鼠和c-KitV922G/+杂合突变小鼠，在进行行为学检测验证抑郁样行为的基础上，1）研究幼年期WKY大鼠在抑郁发生及药物治疗过程中，多巴胺NAc的中型多棘神经元（Medium spiny neurons, MSNs）兴奋性的变化；2）研究成年c-KitV922G/+杂合突变小鼠海马（hippocampus, HP）的CA1区及CA3区突触传递及长时程增强（long-term potentiation, LTP）形成的变化。通过以上检测，我们探讨了NAc的MSNs放电特点及海马神经环路的信号传导变化在抑郁症发病中的作用。主要的方法及结果： 1检测幼年期WKY大鼠在抑郁发生及药物治疗过程中，多巴胺D2类受体（dopamine D2-like receptor）介导的NAc MSNs膜兴奋性的变化。（1）制作4~5周健康雄性WKY大鼠和其正常对照组Wistar大鼠的大脑冠状切片（含有NAc），切片厚度300μm。（2）通过可视化全细胞膜片钳的方法，记录并分析在给予多巴胺D2类受体激动剂喹吡罗（quinpirole）前后，NAc中心核（core）区域的MSNs动作电位的发放情况。在记录过程中，始终在灌流液中加入伽马氨基丁酸A（GABAA）受体阻断剂木防己苦毒素（picrotoxin, PTX）和兴奋性谷氨酸受体阻断剂犬尿喹啉酸（kynurenic acid）。在电流钳模式下给予细胞膜间隔20sec、强度呈步进递增形式的电流刺激，电流强度范围为0-500pA，步幅为50pA，记录其诱发的动作电位数量及产生阈值。结果发现在幼年期WKY大鼠中，多巴胺D2类受体介导的信号通路对NAc core区域的MSNs膜兴奋性的抑制作用缺失；（3）给予幼年期WKY大鼠持续12天的诺米芬新（nomifensine，一种多巴胺和去甲肾上腺素重摄取抑制剂）治疗，通过一系列的行为学检测发现治疗前的WKY大鼠在糖水偏好、开场实验和强迫游泳的行为学实验中均表现出显著的抑郁样行为，而nomifensine治疗后其在糖水偏好和强迫游泳实验中的抑郁样行为显著减少。（4）对治疗后的WKY大鼠NAc core区域的MSNs进行电生理学检测，并与未治疗组的WKY大鼠以及正常对照组Wistar大鼠比较，结果发现在接受nomifensine治疗后WKY大鼠NAc core区域的MSNs膜兴奋性减弱。 2检测成年c-KitV922G/+杂合突变小鼠在抑郁发生过程中，，Mossyfiber-CA3(MF-CA3)和Schaffer collateral-commissural fiber-CA1(Sch-CA1)通路上高频刺激诱导的LTP形成情况。（1）制作2~3月龄的健康雄性c-KitV922G/+杂合突变小鼠和其野生型对照小鼠的急性海马切片，切片厚度400μm。（2）在场电位模式下给予海马切片MF-CA3通路100Hz/1sec两次，以及Sch-CA1通路100Hz/1sec1次的高频刺激，观察LTP的形成情况。实验结束后灌流含有0.1μM DCG IV的人工脑脊液（artificialcerebrospinal fluid, ACSF)，观察突触反应的被抑制情况，以验证所记录的通路确实为MF-CA3。结果发现c-KitV922G/+杂合突变小鼠的MF-CA3通路的LTP形成受损，而Sch-CA1通路的LTP形成未受影响。主要结论：（1）Nomifensine能够改善幼年期WKY大鼠的抑郁样行为；（2）多巴胺D2类受体介导的对MSNs兴奋性的抑制的缺失可能参与幼年期WKY大鼠抑郁样行为的发生。（3）Nomifensine可能通过影响幼年期WKY大鼠海马和纹状体区域的DRD2发挥抗抑郁作用。（4）成年小鼠海马的SCF/c-Kit通路异常对MF-CA3通路LTP形成的抑制，可能参与其学习与记忆的形成障碍。
[Abstract]:Depression is the most prevalent psychiatric disorder in the world today. In China, more than 26 million people suffer from depression, which has the characteristics of high incidence and low diagnostic rate. It has brought serious impact on today's society. Qualitative pathological changes cause great trouble to the study of the pathogenesis of depression and directly affect the development of antidepressants. Therefore, to clarify the pathogenesis of depression and provide effective ideas and methods for the clinical treatment of depression is an urgent scientific question to be solved in the field of psychiatric diseases in China and even in the world. In recent years, more and more attention has been paid to the role of the nucleus accumbens (NAc), an important brain region responsible for reward and addiction mechanisms, in the pathogenesis of depression and antidepressant drugs. NAc is an information-integrating nucleus in the basal nucleus region, which mainly receives information from the ventral tegmental area (VTA). The monoamine hypothesis, one of the hypotheses of depression, holds that dopamine plays an important role in the pathogenesis and antidepressant therapy of depression, but the effect of dopamine on neurological activity in the brain-related areas is still unknown, so if it can be induced from electricity From the point of view of physiology, studying the characteristics of NAc neuronal firing and combining behavioral and biochemical studies can help us understand the role and changes of NAc neuronal activity in the brain dopamine system in the pathogenesis of depression. The mutant mice with a stem cell factor (SCF) and its tyrosine kinase receptor c-Kit pathway dysfunction were electrophysiologically studied. The study of synaptic plasticity in the hippocampus can help us to understand the effect of this gene mutation on synaptic transmission and plasticity in the hippocampus, and explain the reason for the deficiency of learning and memory in the depressive mice from the perspective of electrophysiology.
In this study, we selected Wistar Kyoto (WKY) rats and c-Kit V922G /+ heterozygous mice from two depression models. On the basis of behavioral tests to verify depression-like behavior, we studied the Medium Spiny Neurons (MSN) of dopamine NAc during depression onset and drug treatment in young WKY rats. 2) To study the changes of synaptic transmission and long-term potentiation (LTP) in CA1 and CA3 regions of adult c-KitV922G/+ heterozygous mice hippocampus (HP). The role of.
Main methods and results:
1 To detect the changes of dopamine D2-like receptor-mediated NAc-MSNs membrane excitability during depression and drug therapy in juvenile WKY rats.
(1) Coronary sections (containing NAc) of the brain of healthy male WKY rats and Wistar rats were made at 4-5 weeks and the thickness of the sections was 300 microns.
(2) Visual whole-cell patch clamp technique was used to record and analyze the release of action potential of MSNs in the central nucleus of NAc before and after administration of quinpirol, a dopamine D2 receptor agonist. Xin, PTX and excitatory glutamate receptor blocker kynurenic acid were administered at a 20 sec interval with a step-by-step incremental current stimulus. The current intensity ranged from 0 to 500 pA with a 50 pA stride. The number and threshold of evoked action potentials were recorded in young WKY rats. Dopamine D2 receptor-mediated signaling pathway has no inhibitory effect on the excitability of MSNs membrane in NAc core region.
(3) Treated with nomifensine (a dopamine and norepinephrine reuptake inhibitor) for 12 days in juvenile WKY rats, a series of behavioral tests showed significant depression-like behaviors in glycemic preference, open-field experiment and forced swimming behavior tests in WKY rats before treatment. After treatment with sine, depressive behaviors in sugar water preference and forced swimming test were significantly reduced.
(4) After treatment, MSNs in the NAc core region of WKY rats were detected electrophysiologically, and compared with WKY rats without treatment group and Wistar rats with normal control group. The results showed that the excitability of MSNs membrane in the NAc core region of WKY rats decreased after treatment with nomifensine.
2. To detect the formation of LTP induced by high frequency stimulation in Mossyfiber-CA3 (MF-CA3) and Schaffer collateral-commissural fiber-CA1 (Sch-CA1) pathways during depression in adult c-KitV922G/+ heterozygous mice.
(1) Acute hippocampal slices of healthy male c-KitV922G/+ heterozygous mutant mice aged 2-3 months and wild type control mice were prepared. The slices were 400 microns thick.
(2) The formation of LTP was observed by stimulating the hippocampal MF-CA3 pathway 100 Hz/1 sec twice and the Sch-CA1 pathway 100 Hz/1 sec twice under the field potential mode. It was found that LTP formation in the MF-CA3 pathway was impaired in c-KitV922G/+ heterozygous mice, but not in the Sch-CA1 pathway.
(1) Nomifensine can improve depressive behavior in juvenile WKY rats.
(2) The absence of dopamine D2 receptor-mediated inhibition of MSNs excitability may be involved in the development of depression-like behavior in young WKY rats.
(3) Nomifensine may play an antidepressant role by influencing DRD2 in hippocampus and striatum of juvenile WKY rats.
(4) The abnormal SCF/c-Kit pathway in the hippocampus of adult mice inhibits the formation of LTP in MF-CA3 pathway, which may be involved in the formation of learning and memory disorders.
【学位授予单位】：上海交通大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：R749.41

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