Synaptic mechanisms underlying reward seeking and compulsive drug use

奖励寻求和强迫性药物使用的突触机制

基本信息

批准号：
9155446
负责人：
Veronica A Alvarez
金额：
$ 124.88万
依托单位：
NATIONAL INSTITUTE ON ALCOHOL ABUSE AND ALCOHOLISM
依托单位国家：
美国
项目类别：
财政年份：
资助国家：
美国
起止时间：
至
项目状态：
未结题

来源：
https://reporter.nih.gov/project-details/9155446
关键词：
Acetylcholine Acetylcholinesterase Affect Agonist Agreement Alcohol consumption Amphetamines Animal Model Autoreceptors Basic Science Behavior Behavioral Chemosensitization Cholinergic Receptors Chronic Cocaine Cocaine Abuse Corpus striatum structure Coupled Cues Dependence Depressed mood Development Discrimination Dopamine Dopamine D2 Receptor Dose Drug Addiction Drug effect disorder Drug usage Electric Stimulation Ethanol Feedback Fiber Food Genetic Glutamates Goals Human Image In Vitro Individual Infusion procedures Knockout Mice Link Locomotion Measures Mediating Mental Depression Messenger RNA Midbrain structure Morphology Motivation Mus Muscarinic Acetylcholine Receptor Muscarinic Agonists Muscarinic Antagonists Muscarinic M1 Receptor Muscarinic M2 Receptor Muscarinics Mutant Strains Mice Neurons Nicotinic Receptors Nucleus Accumbens Oxotremorine Pharmaceutical Preparations Physiological Population Presynaptic Terminals Property Regulation Relapse Reporting Research Rewards Role Scanning Scopolamine Self Administration Structure Substance abuse problem Synapses Synaptic Transmission Synaptic plasticity Testing alcohol use disorder behavioral response cholinergic cocaine use craving dopaminergic neuron drug abuser drug seeking behavior improved in vivo incentive salience motivated behavior motor learning neural circuit neurotransmitter release optogenetics presynaptic psychostimulant receptor response stimulant abuse synaptic function tool trait impulsivity transmission process

Acetylcholine Acetylcholinesterase Affect Agonist Agreement Alcohol consumption Amphetamines Animal Model Autoreceptors Basic Science Behavior Behavioral Chemosensitization Cholinergic Receptors Chronic Cocaine Cocaine Abuse Corpus striatum structure Coupled Cues Dependence Depressed mood Development Discrimination Dopamine Dopamine D2 Receptor Dose Drug Addiction Drug effect disorder Drug usage Electric Stimulation Ethanol Feedback Fiber Food Genetic Glutamates Goals Human Image In Vitro Individual Infusion procedures Knockout Mice Link Locomotion Measures Mediating Mental Depression Messenger RNA Midbrain structure Morphology Motivation Mus Muscarinic Acetylcholine Receptor Muscarinic Agonists Muscarinic Antagonists Muscarinic M1 Receptor Muscarinic M2 Receptor Muscarinics Mutant Strains Mice Neurons Nicotinic Receptors Nucleus Accumbens Oxotremorine Pharmaceutical Preparations Physiological Population Presynaptic Terminals Property Regulation Relapse Reporting Research Rewards Role Scanning Scopolamine Self Administration Structure Substance abuse problem Synapses Synaptic Transmission Synaptic plasticity Testing alcohol use disorder behavioral response cholinergic cocaine use craving dopaminergic neuron drug abuser drug seeking behavior improved in vivo incentive salience motivated behavior motor learning neural circuit neurotransmitter release optogenetics presynaptic psychostimulant receptor response stimulant abuse synaptic function tool trait impulsivity transmission process

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项目摘要

Project 1: Muscarinic M5 acetylcholine receptors potentiate synaptic transmission from VTA DA neurons to the NAc (Shin, Adrover, Wess and Alvarez; PNAS 2015) Cholinergic transmission in the striatum functions as a key modulator of dopamine (DA) transmission and synaptic plasticity, both of which are required for reward and motor learning. Acetylcholine (ACh) can elicit striatal DA release through activation of nicotinic ACh receptors (nAChRs) on DA axonal projections. However, it remains controversial how muscarinic ACh receptors (mAChRs) modulate striatal DA release, with studies reporting both potentiation and depression of striatal DA transmission by mAChR agonists. This study investigates the mAChR-mediated regulation of release from three types of midbrain neurons that project to striatum: DA, DA/glutamate, and glutamate neurons. We found that M5 mAChRs potentiate DA and glutamate release only from DA and DA/glutamate projections from the midbrain. We also show that M2/M4 mAChRs depress the nAChR-dependent mechanism of DA release in the striatum. These results suggest that M5 receptors on DA neuron terminals enhance DA release, whereas M2/M4 autoreceptors on cholinergic terminals inhibit ACh release and subsequent nAChR-dependent DA release. Our findings clarify the mechanisms of mAChR-dependent modulation of DA and glutamate transmission in the striatum. Different types of mAChRs (M1-M5) are expressed in the striatum. Gi-coupled M2 receptors are mainly found on presynaptic terminals of CINs and on glutamatergic terminals where they inhibit neurotransmitter release. Gq-coupled M1 receptors are expressed in MSNs, and Gq-coupled M5 receptors are expressed in midbrain DA neurons. Early studies showed that agonists for mAChRs potentiate DA efflux measured in the striatum (de Belleroche and Gardiner, 1982; Lehmann and Langer, 1982; Raiteri et al., 1984). However, DA transients measured using fast-scanning cyclic voltammetry (FSCV) and evoked by electrical stimulation are depressed by mAChR agonists (Kudernatsch and Sutor, 1994; Bendor et al., 2010; Foster et al., 2014). The hypothesis of this study is that agonists for mAChRs have different effects on DA transients evoked by electrical stimulation (eDA) within the NAc compared to DA transients evoked by direct optogenetic activation of DA fibers (oDA) because electrical stimulation drives both ACh-mediated and monosynaptic DA release. This study investigates the modulation of DA transmission by mAChRs when using conventional electrical stimulation and optogenetic stimulation to selectively activate VTA DA neuron fibers. Channelrhodopsin-2 was expressed in DA neurons in the VTA and DA transients were evoked by alternating electrical stimulation with optogenetic stimulation to trigger eDA and oDA transients, respectively. In agreement with previous observations, eDA transients were depressed by 70% by the muscarinic agonist oxotremorine. In contrast, the same concentration of oxotremorine potentiated oDA transients by 20%. These results indicate that a muscarinic agonist has opposite effects on DA transients evoked by electrical stimulation, which involves activation of CINs versus DA transients evoked by optogenetic stimulation that directly activates DA fibers. VTA DA neurons that project to the NAc shell co-release glutamate. Indeed, oxotremorine potentiated oEPSC by 56%) while inhibiting electrically evoked EPSCs recorded on MSNs in the NAc shell, which are largely mediated by activation of cortical synapses that express presynaptic M2 receptors. The potentiation was completely reversed by application of the muscarinic antagonist, scopolamine, and it was totally absent in M5 receptor knockout mice, demonstrating that M5 mAChRs, presumably located in presynaptic DA neurons, are required for the potentiation of neurotransmitter release from DA terminals. Inhibition of acetylcholinesterase activity by application of the selective blocker ambenonium produced robust enhancement of oDA transients, demonstrating that endogenous ACh potentiates DA transmission from midbrain DA terminals. Taken together, our results suggest that the muscarinic receptor M5 potentiates DA and glutamate transmission from midbrain DA neurons in the NAc. Whereas, mAChR agonist decreases eDA transients through activation of mAChRs on CINs, which in turn dampens ACh release and decreases DA and glutamate release from DA terminals. Project: D2 autoreceptors control the reinforcing properties of cocaine and the reactivity to drug-paired cues (Holroyd et al., Neuropsychopharmacology 2015) A prominent aspect of drug addiction is the ability of drug-associated cues to elicit craving and facilitate relapse. In human drug abusers, the presentation of drug-associated cues, such as drug paraphernalia, can trigger large increases in DA in the striatum even in the absence of the drug (Volkow et al., 2006). An abundance of studies have demonstrated a link between low levels of striatal D2 receptors and cocaine abuse, high craving and increased relapse both in humans (Volkow et al., 1997; Volkow et al., 2009) and animal models (Nader et al., 2006; Dalley et al., 2007; Belin et al., 2008). However, the contribution of D2Rs of non-striatal origin to cocaine seeking and the liability for cocaine abuse has been overlooked and is not clearly understood. A recent imaging study in humans showed that low levels of midbrain D2 receptor availability correlates with increased subjective responses to amphetamine and impulsivity traits, two strong predictors for developing substance abuse (Zald et al., 2008; Buckholtz et al., 2010). Animal models and basic research on midbrain D2 receptors in relation to these cocaine behaviors is notably absent. The hypothesis of this study is that D2Rs of non-striatal origin, such as those expressed by midbrain DA neurons, modulate the behavioral responses to cocaine by altering its reinforcing properties and the response to drug-paired cues. D2Rs in DA neurons function as autoreceptors exerting feedback inhibition over DA neuron excitability and DA release. To test this, we took advantage of our recently generated conditional mutant mouse strain selectively lacking D2 autoreceptors (autoDrd2KO) while preserving normal levels of Drd2 mRNA in the striatum (Bello et al., 2011). We showed that selective loss of D2 autoreceptors impairs the feedback inhibition of DA release and amplifies the cocaine effect on DA transients in the NAc. Interestingly, mice lacking D2 autoreceptors were more likely to acquire cocaine self-administration than controls. However, acquisition of cued-operant responding for a food reward was similar in autoDrd2KO mice and controls, indicating a selective vulnerability for psychostimulants. The enhanced acquisition for cocaine seen in autoDrd2KO mice is due to a combination of a higher rate of cocaine infusions and an improved discrimination between the active and inactive holes during the first week of self-administration. The dose dependence of responding for cocaine and the breakpoint values were similar to controls, suggesting that cocaine sensitivity and the motivation to seek cocaine were not altered. Further, autoDrd2KO mice showed a heightened response to cocaine-paired cues, indicating that they attribute enhanced incentive salience to cocaine-paired cues. Cue-induced reinstatement was also stronger in autoDrd2KO mice, suggesting that the enhanced reactivity to cocaine-paired cues is sufficient to trigger drug-seeking behavior even in the absence of the drug, which resembles a critical feature observed in humans that abuse psychostimulants. Altogether, this study shows that D2 autoreceptors can contribute to the vulnerability for cocaine use and relapse by enhancing the reinforcing properties of cocaine and the salience of drug-paired cues.

项目1：毒蕈碱M5乙酰胆碱受体增强了从VTA DA神经元到NAC的突触传播（Shin，Adrover，Wess和Alvarez; PNAS; PNAS 2015）纹状体中的胆碱能传播是多巴胺（DA）传播和突触可塑性的关键调节剂，这两者都是奖励和运动学习所必需的。乙酰胆碱（ACH）可以通过在DA轴突投影上激活烟碱ACH受体（NACHR）引起纹状体DA释放。但是，毒蕈碱ACH受体（MACHRS）如何调节纹状体DA释放，这仍然是有争议的，研究报告了MACHR激动剂传播纹状体DA传播的增强和抑郁。这项研究调查了MACHR介导的调节从三种将纹状体的中脑神经元释放的调节：DA，DA/谷氨酸和谷氨酸神经元。我们发现，M5 MACHR仅从中脑从DA和DA/谷氨酸投影中释放DA和谷氨酸。我们还表明，M2/M4 MACHR降低了纹状体中DA释放的NACHR依赖性机理。这些结果表明，DA神经元末端上的M5受体增强了DA释放，而M2/M4自身受体上的胆碱能末端受体抑制ACH释放，随后NACHR依赖性DA释放。我们的发现阐明了纹状体中DA和谷氨酸传播的MACHR依赖性调制的机制。不同类型的MACHR（M1-M5）在纹状体中表达。 GI偶联的M2受体主要在CINS和谷氨酸能末端的突触前末端发现，它们抑制神经递质释放。 GQ耦合的M1受体在MSN中表达，GQ耦合的M5受体在中脑DA神经元中表达。早期研究表明，MACHRS的激动剂增强了在纹状体中测得的DA外排（De Belleroche和Gardiner，1982； Lehmann and Langer，1982； Raiteri等，1984）。然而，使用快速扫描的循环伏安法（FSCV）测量并被电刺激引起的DA瞬变会被MACHR激动剂抑制（Kudernatsch和Sutor，1994; Bendor等，2010; Foster等，2014）。这项研究的假设是，与通过直接光遗传学激活DA纤维（ODA）引起的DA瞬变相比，NAC中的电刺激（EDA）对DA瞬变具有不同的影响，因为电刺激驱动ACH介导的ACH介导的和单次触及DA的释放。这项研究调查了MACHR对DA传播的调节，当使用常规的电刺激和光遗传刺激以有选择地激活VTA DA神经元纤维。在VTA中的DA神经元中表达了通道Rhodopsin-2，通过与光遗传学刺激交替刺激以触发EDA和ODA瞬变，唤起了DA瞬变。与先前的观察结果一致，毒蕈碱激动剂氧氨酸人群使EDA瞬变降低了70％。相比之下，相同浓度的低氧蛋白浓度使ODA瞬变增强了20％。这些结果表明，毒蕈碱激动剂对通过电刺激引起的DA瞬变具有相反的影响，这涉及CINS激活CINS与原始刺激引起的DA瞬变，该瞬变直接激活DA纤维。 VTA DA神经元，该神经元将投射到NAC Shell共同释放谷氨酸。实际上，氧化脱毛的OEPSC增强了56％），同时抑制了NAC壳中MSN上记录的电诱发的EPSC，该EPSC在NAC壳中的MSN上记录了，这些EPSC在很大程度上是通过表达突触前M2受体的皮质突触激活而介导的。通过施用毒蕈碱拮抗剂，scopolamine可以完全逆转这种增强作用，并且在M5受体敲除小鼠中完全不存在，这表明可能位于突触前DA神经元中的M5 MACHR是从Da terminals释放Neurotransmitter所必需的。通过应用选择性阻滞剂Ambenium抑制乙酰胆碱酯酶活性可产生ODA瞬变的强大增强，这表明内源性ACH增强了从中脑DA末端的DA传播。综上所述，我们的结果表明，毒蕈碱受体M5从NAC中的中脑DA神经元增强了DA和谷氨酸的传播。而MACHR激动剂通过CINS上的MACHR激活降低EDA瞬变，从而减少ACH释放并减少DA末端的DA和谷氨酸释放。项目：D2自身受体控制可卡因的增强特性和对药物培养线索的反应性（Holroyd等，Neuropsychopharmacology 2015）药物成瘾的一个重要方面是药物相关线索引起渴望和促进复发的能力。在人类药物滥用者中，即使在没有药物的情况下，与药物相关的提示（例如药物用具）也可能引发纹状体的大量增加（Volkow等，2006）。大量的研究表明，低水平的纹状体D2受体与可卡因滥用，高渴望和人类的复发增加（Volkow等，1997; Volkow等，2009）和动物模型（Nader等，2006; Dalley等，2007; Belin等，2007; Belin等人，2008年）。但是，非纹状体起源的D2RS对可卡因寻求和可卡因滥用的责任的贡献已被忽略，尚未清楚地理解。人类最近的一项成像研究表明，低水平的中脑D2受体的可用性与对苯丙胺和冲动性状的主观反应增加相关，这是发展药物滥用的两个强有力的预测因子（Zald等，2008; Buckholtz等，2010）。动物模型和关于中脑D2受体与这些可卡因行为有关的基础研究非常不存在。这项研究的假设是，非纹状体起源的D2R，例如中脑DA神经元表达的D2R，通过改变其加强特性和对药物对培养线索的反应来调节对可卡因的行为反应。 DA神经元中的D2Rs充当自身受体，对DA神经元兴奋性和DA释放的反馈抑制作用。为了测试这一点，我们利用了我们最近生成的有条件突变小鼠菌株选择性地缺乏D2自身受体（AUTODRD2KO），同时保留了纹状体中正常水平的DRD2 mRNA水平（Bello等，2011）。我们表明，D2自动受体的选择性损失会损害DA释放的反馈抑制，并扩大可卡因对NAC中DA瞬变的影响。有趣的是，缺乏D2自身受体的小鼠比对照组更可能获得可卡因自我给药。但是，在AutoDRD2KO小鼠和对照组中，获取对食物奖励的提示术反应相似，这表明对精神刺激剂的选择性脆弱性。在AutoDRD2KO小鼠中看到的可卡因的获取增强是由于在自我管理的第一周内，可卡因输注率更高的速率和在主动孔和非活动孔之间的歧视相结合。对可卡因和断点值的反应的剂量依赖性与对照相似，这表明可卡因敏感性和寻求可卡因的动机没有改变。此外，AutoDRD2KO小鼠对可卡因配对提示的反应增强，这表明它们将增强的激励显着性归因于可卡因生成的提示。在AutoDRD2KO小鼠中，提示引起的恢复也更强，这表明对可卡因生成的提示的反应性增强也足以触发毒品的行为，即使没有药物，这种行为类似于在人类中观察到的滥用精神抑制剂的关键特征。总而言之，这项研究表明，D2自身受体可以通过增强可卡因的加强特性和药物培养线索的显着性来促进可卡因使用和复发的脆弱性。