慢性应激性抑郁大鼠胃运动变化中海马谷氨酸代谢1型受体和多巴胺D1受体的关系

【作者】 吴艳艳；

【导师】 安书成；

【作者基本信息】 陕西师范大学 ， 神经生物学， 2010， 硕士

【摘要】 抑郁症(depression)是一种常见的精神疾病,以食欲不振、心情压抑、兴趣丧失、精力不足、自我评价过低及体重下降、失眠、疲劳、无望感及自杀倾向等为主要表现。其广泛性、易复发性及自杀倾向严重影响着患者工作、学习和社会职能的发挥。在抑郁症复杂多源的发病机制中,应激(stress)是一个不可忽视的重要因素,因为应激环境或者应激因子通常先于抑郁症状存在；抑郁症患者的应激因素明显多于一般人群。功能性胃肠疾病(FGID)的发病机制与精神、应激因素有着紧密相联的关系,病人的性格异常、焦虑、抑郁积分明显高于正常人。中枢神经系统中,海马属于边缘前脑,是与学习、记忆和情绪行为功能密切相关的重要脑区,对情绪反应和胃肠活动都有着重要的调控作用,也是应激易累及损伤的主要靶区；同时,海马富含各种神经递质的受体,是应激激素作用的靶区,也是具有可塑性和极易受损的脑区。目前有研究显示,在慢性应激时,海马谷氨酸(glutamate,Glu)水平长期显著高于基础值。谷氨酸是哺乳动物中枢神经系统重要的兴奋性神经递质,参与了学习、记忆、药物依赖成瘾及神经系统退行性疾病等多种病理生理过程。在应激性脑损伤中,对于谷氨酸通过受体介导的神经毒作用,以往的研究主要集中在谷氨酸离子型受体上。随着20世纪80年代代谢型谷氨酸受体(mGluRs)的发现,mGluRs在应激性脑损伤的作用也日渐受到重视。应激过程中脑皮质内Glu含量的升高曲线与mGluR1表达合成增加趋势基本吻合,提示Glu可能通过其受体mGluR1产生的神经毒作用参与了应激源对中枢神经系统的损害作用。近年来在脑创伤的实验研究中,也开始有应用mGluR1的拮抗剂AIDA进行神经保护的研究,例如Meli等对体外培养的神经细胞、大鼠海马区脑组织造成缺氧和缺糖的损伤研究,发现mGluR1的拮抗剂AIDA能缓解损伤导致的神经细胞数目下降,而激动剂能加重神经细胞损伤。多巴胺(dopamine,DA)是20世纪研究的最有成效的脑内神经递质之一,也是一种重要的胃肠道神经递质。DA参与和影响脑及躯体的生理功能是广泛并且值得受到关注的,它参与调控运动功能并且参与情绪和认知能力,也可调节心血管和胃肠功能。有研究表明,DA在抑郁症的发病和治疗中也起着重要作用,抑郁症患者DA功能减退,而增高DA的浓度的药物如酪氨酸、苯丙胺则能缓解抑郁症状。多巴胺的D1受体在多巴胺改善抑郁样行为中发挥着关键性的作用,例如,选择性D1受体激动剂在无助模型和强迫游泳实验中均表现出了抗抑郁的作用,而当用SCH23390阻断D1受体后阻断了丙咪嗪的治疗作用。这说明D1受体参与了丙咪嗪的抗抑郁作用。Ossowska等研究发现,长期应激处理后的大鼠边缘系统的D1受体密度显著增加,而通过长期抗抑郁药物的治疗则可产生相反的作用。这又进一步证明了D1受体参与了抑郁症的发病机制。有研究显示,在皮质纹状体激活mGluI型受体而不是Ⅱ、Ⅲ型受体,减少多巴胺的释放是剂量依赖性的,而当阻断mGluI型受体后则没有这种效果。近期有实验研究表明,Ⅰ型代谢型谷氨酸受体直接提高了海马单胺类递质的水平：mGlul受体阻断剂AIDA增强了DA的水平。因此本实验提出mGlul受体拮抗剂能否起到抗抑郁样作用以及对胃活动有何影响,这些作用是否通过提高DA的水平来完成,而DA的这种作用是否通过D1受体来实现,换言之,谷氨酸通过mGlul受体引起抑郁的作用是否通过降低了DA的表达来实现,据此本实验通过建立慢性不可预见性温和应激(Chronic unpredicted mild stress,CUMS)抑郁大鼠模型,海马微量给药,观测动物行为变化且记录胃运动,探讨mGluR1与抑郁症的关系及其对胃运动的影响,揭示mGluR1与多巴胺D1受体在应激性抑郁发生中对胃活动调节中的关系,证明mGluRl的作用是否通过多巴胺的D1受体来实现。实验结果如下：1.CUMS处理后,与正常对照组相比,大鼠体重增长率、糖水偏好率、敞箱实验的水平得分、垂直运动得分显著降低(P<0.01),游泳不动时间显著延长(P<0.05),同时大鼠平均胃内压和胃的收缩幅值也显著降低(P<0.01)。2.海马微量注射Glu与CUMS引起的动物行为表现一致,与正常对照组相比,大鼠体重增长率(P<0.01)、糖水偏好率(P<0.05)、敞箱实验的垂直运动得分显著降低(P<0.01),同时海马微量注射Glu可明显降低大鼠的胃内压(P<0.01)和胃收缩幅值(P<0.05)。3.海马微量注射mGlul受体阻断剂AIDA可消除应激所引起的体重增长率(P<0.01)、糖水偏好率(P<0.05)、水平运动(P<0.01)、垂直运动(P<0.05)得分的减少,游泳不动时间与CUMS组相比,极显著减少(P<0.01)。对大鼠进行21d慢性不可预见性应激的同时,海马微量注射mGluRl受体的阻断剂AIDA可明显改善慢性应激引起的胃活动减弱作用,与CUMS组相比,有显著性差异(P<0.05)。4.海马预先注射mGlul受体阻断剂AIDA,再注射Glu,大鼠的体重增长率、糖水偏爱率、水平得分都有所增加,但差异不显著,垂直运动得分显著增加(P<0.01),游泳不动时间显著减少(P<0.01),海马微量注射AIDA+Glu组与Glu组相比较,胃内压和胃收缩幅值有所增强,但是差异不显著。5.慢性不可预见性温和应激21d,海马微量注射AIDA的同时注射SCH-23390(D1受体阻断剂),与AIDA+CUMS相比,体重增长率(P<0.01)、糖水偏爱率(P<0.01)、水平得分(P<0.05)、垂直运动(P>0.05)降低,游泳不动时间显著增加(P<0.01)。胃内压减小而胃收缩幅值大于AIDA+CUMS组,但无显著性差异。从本实验结果可以得出,CUMS应激诱发抑郁,而抑郁既有行为学表现,又有胃肠活动的显著减弱,应激引起情绪变化是胃肠功能紊乱的原因之一。海马是应激反应发生的主要神经核团,海马过量的Glu既具有产生抑郁的作用,又有抑制胃肠活动的作用,而这些作用都能被mGluR1受体阻断剂AIDA所减弱,不能完全消除,说明过量的Glu引起抑郁样行为表现部分是通过mGluR1受体实现的。当然,还有其他受体也参与了抑郁行为。在注射AIDA的同时给予SCH-23390,AIDA的抗抑郁作用有所削弱,而胃收缩反而有所加强。这表明慢性应激引起抑郁样行为变化和胃活动抑制的神经机制有所不同,过量Glu经mGluR1受体抑制DA释放可能是产生抑郁样行为的原因之一,而对胃活动的抑制似乎与DA及其D1受体关系不大。总之,情绪变化和胃运动之间的关系非常密切同时也十分复杂,对于其具体的机制还需继续深入的研究。更多还原

【Abstract】 Depression is a common mental illness,the main performance of which is poor appetite, depressed mood, loss of interest, low energy, low self-evaluation and weight loss, insomnia, fatigue, hopelessness, and suicidal tendencies. Its universality, easy, and recurrent suicidal tendencies in patients with a serious impact on learning, work and social functions of play. In the complex mechanism of depression,the stress is an important factor can not to be ignored, because:stress factor or the stress environment often exist precedes depressive symptoms; the stress factors in patients with depression was higher than the general population. The incidence and spirit of functional gastrointestinal disorders (FGID) are closely related to stress factors, the patient’s personality abnormalities, anxiety, depression, significantly higher than the normal human. In the central nervous system, the hippocampus,one part of limbic forebrain, is associated with learning, memory and emotional behavior, has an important regulatory role in emotional reactions and gastrointestinal activity, is also main target to stress injuries. At the same time, the hippocampus is rich in a variety of messenger receptor, is the target area of stress hormones and is also with the plasticity and easily damaged.There are research reports indicate that under chronic stress, the hippocampus glutamic acid (glutamate, Glu) levels were significantly higher than the basis of the long-term value. Glutamate is an important excitatory neurotransmitter in mammalian central nervous system involved in learning, memory, drug addiction and nervous system rely on a variety of degenerative diseases. In the stress-induced injury, the glutamate receptor mediates neurotoxic effects by receptors, previous studies focused on ionotropic glutamate receptors. As in the 1980s of metabotropic glutamate receptors (mGluRs) found, mGluRs in the stress-induced brain injury is also increasing attention. The increase of Glu content in cerebral cortex during stress agrees with the expression of mGluRl synthesis curve, suggesting that Glu may be generated Neurotoxicity through the mGluR1 receptors involved in the damage of central nervous system produced by stressors. In the experimental study of traumatic brain injury in recent years have started to use AIDA for neuroprotective studies, Meli,etc. For example, nerve cells in vitro rat hippocampus region of brain tissue caused by hypoxia and hypoglycemia injury and found that mGluR1 antagonist AIDA can reduce the decline in the number of nerve cells caused by damage, while the agonists can aggravate nerve cell damage. Dopamine (DA) is one of the most effective brain neurotransmitter be studied in 20th century, DA participate and influence the physiological functions of the brain and body is an important and wide-ranging, and regulation of motor function and participation in emotional and cognitive abilities, and also can be adjusted to cardiovascular and gastrointestinal function. Some studies have shown, DA plays an important role in the pathogenesis and treatment of depression, DA dysfunction in patients with depression while increase the concentration of DA drugs such as tyrosine, amphetamine can ease symptoms of depression. DA is one of the most effective study of the brain neurotransmitter currently, is also an important neurotransmitter in the gastrointestinal tract. Dopamine D1 receptor plays a crucial role in improving depression-like behavior of dopamine,for example, the selective D1 receptor agonist in helplessness model and the forced swim test have shown the antidepressant effect, and when the D1 receptor blockade with SCH23390 showed blocking the treatment of imipramine. This indicates that D1 receptors are involved in the antidepressant effects of imipramine. Other study by Ossowska found that under long-term stress treatment, D1 receptor density increased significantly in the limbic system, while through long-term treatment with antidepressants may have the opposite effect. This is further proof of the D1 receptors involving in the pathogenesis of depression. This is further proof of the D1 receptors are involved in the pathogenesis of depression.Therefore, this study proposed whether mGlul receptor antagonist could display antidepressant-like effect and how to impact on gastric activity, whether these effects are accomplished through increased DA and DA in this role is achieved through the D1 receptor, in other words, whether depression caused by mGlu1 receptor is through reducing the DA to achieve. In this study, through the establishment of chronic unpredictable mild stress (CUMS) rat model of depression, hippocampus trace administration, observation of animal behavior and record changes in gastric motility, to explore the the relationship between mGluRl antagonist AIDA and depression and its impact on gastric motility, as well as reveal whether the role of AIDA in this effect through dopamine D1 receptors to achieve, as to provide the experimental basis whether involved in the regulation of indigestion due to stress-induced. The results are as follows:1.CUMS treatment, compared with normal control group, body weight growth rate, sugar preference rate, the level of open-field test scores, vertical motion scores significantly lower (P <0.01),swimming immobility time was significantly prolonged (P<0.05), while rats with mean intragastric pressure and gastric contraction amplitude was significantly lower (P<0.01).2.Hippocampal microinjection of Glu and CUMS animals caused by the same behavior, compared with normal control group, body weight growth rate (P<0.01),sugar preference rate (P <0.05),open-field test of the vertical movement scores are significantly decreased (P<0.01),while microinjection of Glu in hippocampus of rats can be significantly reduced intragastric pressure (P <0.01)and gastric contraction amplitude (P<0.05).3.Hippocampal microinjection of AIDA (mGlul receptor antagonist) can eliminate weight growth rate (P<0.01),sugar preference rate (P<0.05), horizontal movement (P<0.01),vertical movement (P<0.05)scores caused by stress. Swimming immobility time compared with the CUMS very significantly reduced (P<0.01).Under 21d chronic unpredictable mild stress, hippocampus microinjection of mGluR1 receptors antagonist AIDA can significantly improve the chronic stress-induced weakening of activity in the role of the stomach, compared with CUMS, there is a significant difference (P<0.05).4. Pre-injection of the hippocampus AIDA (mGlul receptor antagonist) re-injection of Glu, rat body weight growth rate, sugar preference rate, the level of rates have increased, but the difference was not significant, vertical motion score increased significantly (P<0.01),swimming immobility time significantly reduced (P<0.01),hippocampal microinjection of AIDA+Glu group compared with the Glu group, intragastric pressure and gastric contraction amplitude was enhanced, but no significant difference.5.Chronic unpredictable mild stress-21d at the same time, the hippocampus, microinjection of SCH-23390 (D1 receptor antagonist) while injection of AIDA, as compared with the AIDA+CUMS group, weight growth rate (P<0.01),sugar preference rate (P<0.01),horizontal movement (P<0.05), vertical movement (P<0.05) reduced, immobility time in swimming increased significantly (P<0.01). Intragastric pressure and gastric contraction amplitude were higher than AIDA+CUMS group, but not significantlyThe experimental results can be drawn from this, CUMS induces depression, and depression performs both behavioral and gastrointestinal activity reduced, stress-induced mood change is one of the causes in gastrointestinal disorders. Hippocampus is a major stress reaction nerve nucleus, excessive Glu in hippocampus has both created the role of depression and inhibit gastrointestinal motility. These effects can be weakened by mGluR1 receptor antagonist AIDA and can not be eliminated completely explain depression-like behavior caused by excessive Glu is some kind achieved through the mGluRl receptor. Of course, there are other receptors are also involved in depression behavior. AIDA injection at the same time giving SCH-23390, results showed that, the antidepressant effect of AIDA has been weakened. But gastric contraction has been enhanced. This indicates that neural mechanisms of chronic stress-induced depression-like changes in behavior and gastric inhibitory activities are different. Excessive Glu release by mGluR1 receptors to inhibit DA produces depression-like behavior may be one of the reasons. The inhibition of gastric activity has little to do wit the DA and the D1 receptor. In short, the relationship between the mood changes and gastric motility is very closely and complexity, the specific mechanism needs to be continue in-depth studied.更多还原