Basic brain mechanisms underlying drug addiction, craving, and relapse

药物成瘾、渴望和复发的基本大脑机制

• 批准号: 9155741
• 负责人: Eliot Gardner
• 金额: $ 29.07万
• 依托单位: NATIONAL INSTITUTE ON DRUG ABUSE
• 依托单位国家: 美国
• 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/9155741
• 关键词: AM630; Addictive Behavior; Agonist; Alcohols; Animal Model; Animals; Area; Attenuated; Beer; Behavior; Behavioral; Behavioral Model; Biochemical; Biological Assay; Biological Models; Blood; Brain; CNR1 gene; CNR2 gene; Cannabinoids; Characteristics; Choice Behavior; Cocaine; Consumption; Cues; Dependence; Development; Dopamine; Drug Addiction; Electrical Stimulation of the Brain; Endocannabinoids; Ethanol; Exposure to; Food; Genes; Goals; High Pressure Liquid Chromatography; Hour; Human; Immune system; Immunoblotting; Impulsivity; Incentives; Intention; Intravenous; Knowledge; Laboratories; Laboratory Animals; Laboratory Rat; Link; Locomotion; Measures; Mediating; Mental Depression; Microdialysis; Microinjections; Modeling; Motivation; Mus; Neuraxis; Nucleus Accumbens; Pharmaceutical Preparations; Pharmacotherapy; Polymerase Chain Reaction; Proteins; Psychological reinforcement; RNA; Receptor Gene; Relapse; Reporting; Research; Resources; Reverse Transcription; Rewards; Sampling; Self Administration; Self-Administered; Stress; Symptoms; Synapses; System; Techniques; Testing; Therapeutic; Time; Western Blotting; Wild Type Mouse; Work; addiction; binge drinking; clinically relevant; craving; discounting; dopamine system; drinking; drinking water; extracellular; in vivo; insight; interest; neurochemistry; novel; pre-clinical; preference; relating to nervous system; research study

During the present reporting period, our research in this area was limited due to severe reductions in available research resources. Nevertheless, we carried out research in three distinct domains - first, continued research into the existence of cannabinoid CB2 receptors in the brain, second, preliminary experiments with a reward delay discounting behavioral model, and third, setting up an alcohol binge-drinking behavioral model in our laboratory. In the cannabinoid and endocannabinoid realm of research, the existence of cannabinoid CB2 receptors in the brain has been heretofore controversial. Most evidence has heretofore suggested that only CB1 cannabinoid receptors are found in brain and central nervous system while cannabinoid CB2 receptors are restricted to the body's periphery - primarily in the immune system. However, this view has been challenged by recent claims that CB2 receptors are present in the central nervous system and by recent claims that CB2 receptors modulate synaptic activity. Therefore, we used highly selective CB2 agonists and antagonists, combined with the use of CB1 and CB2 receptor gene-deleted mice, to study CB2 involvement in cocaine's behavioral and neurochemical effects. We found that the CB2 receptor-selective agonist JWH133 attenuates intravenous cocaine self-administration in wild-type and CB1 gene-deleted mice, but not in CB2 gene-deleted mice. This effect was abolished by the CB2 receptor-selective antagonist AM630. To confirm our findings, we also used the CB2-selective agonist GW405833 and found a similar inhibition of intravenous cocaine self-administration in wild-type mice. Under progressive-ratio reinforcement conditions, we found that JWH133 inhibits incentive motivation to self-administer cocaine, as evidenced by strong reductions in the progressive-ratio break-point. Similar effects were found when JWH133 was administered intra-nasally (for direct passage into the brain via the cribiform plate) or administered by direct intracerebral microinjections of JWH133 into the nucleus accumbens. Again, the effect was seen in wild-type but not in CB2 receptor gene-deleted mice. JWH133 by itself was found to have no reinforcing or aversive effects, as assessed by intravenous self-administration and by conditioned place preference/aversion experiments. Further, JWH133 inhibited cocaine-enhanced locomotion in wild-type and CB1 gene-deleted mice, but not in CB2 gene-deleted mice. JWH133 by itself had an inhibitory effect on locmotion, both with systemic administration and with intracerebral microinjection into the nucleus accumbens in wild-type and CB1 gene-deleted mice, but not in CB2 gene-deleted mice. The CB2 selective antagonist AM630 had a stimulatory effect on locomotion, both with systemic administration and with intracerebral microinjection into the nucleus accumbens in wild-type and CB1 gene-deleted mice, but not in CB2 gene-deleted mice. JWH133 by itself inhibited extracellular nucleus accumbens dopamine as measured by real-time in vivo brain microdialysis. JWH133 also inbited basal and cocaine-enhanced extracellular nucleus accumbens dopamine as measured by real-time in vivo brain microdialysis. This effect was blocked by the CB2-selective antagonist AM630. By itself, AM630 - microinjected intracerebrally into the nucleus accumbens - aumented basal extracellular nucleus accumbens dopamine. We conclude that CB2 cannabinoid receptors exist in the brain, that CB2 receptors functionally modulate the meso-accumbens dopamine system, that CB2 receptors functionally modulate dopamine-mediated behaviors, and that the brain CB1 and CB2 receptor-linked neural systems may functionally antagonize each other in a reciprocal mutually antatagonistic manner. Such mechanistic knowledge can aid in the search for new and effective pharmacotherapeutic compounds for the treatment of drug addiction and dependence. In addition, during this reporting period, we carried out preliminary experiments with a reward-delay-discounting animal model of addiction. At the human level, inability to delay gratification is a pathognomonic symptom of drug addiction. Therefore, we added the reward-delay-discounting task to our battery of preclinical animal models. In this task, laboratory rats are presented with two wall-mounted levers in their test chambers. Depression of one lever delivers a food reward immediately. Depression of the other lever delivers a larger reward after a delay period ranging up to 60 seconds. The animal must choose whether it desires a small immediate reward or a larger delayed reward. In this manner, impulsive choice can be measured and quantified. This model gives us an entirely new clinically-relevant perspective to evaluate potentially therapeutic anti-addiction anti-craving anti-relapse medications at the preclinical animal model level. Using this model during the reporting period, we found that laboratory rats self-assort themselves bimodally into animals with high impulsive choice and others with low impulsive choice. We further found that in the high impulsive choice animals, cocaine produces a shift toward less impulsivity. In contrast, in the low impulsive choice animals, cocaine produces a shift toward higher impulsivity. We intend to further explore the effects of addictive drugs on impulsive choice behavior using this new animal model. In addition, during this reporting period, we introduced an alcohol binge-drinking animal model into our battery of preclinical animal models of addiction. At the human level, binge-type drug taking behavior is often characteristic of drug addiction. Therefore, we have added an alcohol binge-drinking animal model. In this task, laboratory rats are allowed to drink water, near beer (containing no ethanol), or beer (containing 2% ethanol) for 2 hours per day. Binge drinking is operationally defined as bringing blood ethanol levels up to at least 80mg/dl within 2 hours of the initial drink. It is our intention to use this new animal model to determine whether any of our putative anti-addiction pharmacotherapies can alter binge drinking in a putatively therapeutic direction. We believe that the addition of this new model gives us yet another new clinically-relevant perspective to evaluate potentially therapeutic anti-addiction anti-craving anti-relapse medications at the preclinical animal model level. If successful, we intend to investigate binge consumption of other addictive drugs.

在本报告期内，由于可用研究资源严重减少，我们在这一领域的研究受到限制。尽管如此，我们在三个不同的领域进行了研究——第一，继续研究大脑中大麻素 CB2 受体的存在，第二，奖励延迟​​贴现行为模型的初步实验，第三，在我们的实验室建立酗酒行为模型。在大麻素和内源性大麻素的研究领域，大麻素 CB2 受体在大脑中的存在迄今一直存在争议。迄今为止，大多数证据表明，仅在大脑和中枢神经系统中发现了 CB1 大麻素受体，而大麻素 CB2 受体仅限于身体的外周 - 主要是在免疫系统中。然而，这种观点受到最近关于 CB2 受体存在于中枢神经系统中的说法以及最近关于 CB2 受体调节突触活动的说法的挑战。因此，我们使用高选择性的CB2激动剂和拮抗剂，结合使用CB1和CB2受体基因缺失的小鼠，研究CB2参与可卡因的行为和神经化学作用。我们发现，CB2 受体选择性激动剂 JWH133 会减弱野生型和 CB1 基因缺失小鼠的静脉内可卡因自我给药，但不会减弱 CB2 基因缺失小鼠的静脉注射可卡因。这种效应被 CB2 受体选择性拮抗剂 AM630 消除。为了证实我们的发现，我们还使用了 CB2 选择性激动剂 GW405833，并发现野生型小鼠静脉注射可卡因自我给药具有类似的抑制作用。在渐进比率强化条件下，我们发现 JWH133 抑制自我施用可卡因的激励动机，渐进比率断点的大幅降低证明了这一点。当 JWH133 鼻内给药（通过筛板直接进入大脑）或通过直接脑内显微注射 JWH133 进入伏隔核时，发现了类似的效果。同样，这种效应在野生型小鼠中出现，但在 CB2 受体基因缺失的小鼠中却没有出现。通过静脉自我给药和条件性位置偏好/厌恶实验评估，发现 JWH133 本身没有增强或厌恶作用。此外，JWH133 可以抑制野生型和 CB1 基因缺失小鼠中可卡因增强的运动，但不能抑制 CB2 基因缺失小鼠中的运动。 JWH133 本身对野生型和 CB1 基因缺失小鼠的全身给药和伏核脑内显微注射均具有运动抑制作用，但在 CB2 基因缺失小鼠中则没有。 CB2选择性拮抗剂AM630对野生型和CB1基因缺失小鼠的全身给药和伏核脑内显微注射均具有运动刺激作用，但在CB2基因缺失小鼠中则不然。通过实时体内脑微透析测量，JWH133 本身抑制细胞外伏隔核多巴胺。通过实时体内脑微透析测量，JWH133 还抑制基础多巴胺和可卡因增强的细胞外伏核多巴胺。这种效应被 CB2 选择性拮抗剂 AM630 阻断。 AM630 本身——通过脑内显微注射到伏隔核中——增强了基底细胞外伏隔核多巴胺。我们得出结论，CB2大麻素受体存在于大脑中，CB2受体功能性调节中伏隔多巴胺系统，CB2受体功能性调节多巴胺介导的行为，并且大脑CB1和CB2受体相关的神经系统可能以相互拮抗的方式在功能上相互拮抗。这种机制知识可以帮助寻找新的有效的药物治疗化合物来治疗药物成瘾和依赖性。此外，在本报告期内，我们对成瘾的奖励-延迟-折扣动物模型进行了初步实验。在人类层面上，无法延迟满足是吸毒成瘾的一个典型症状。因此，我们将奖励延迟折扣任务添加到我们的临床前动物模型中。在这项任务中，实验室老鼠的测试室内有两个壁挂式杠杆。按下一个杠杆会立即提供食物奖励。 在长达 60 秒的延迟期后，按下另一个控制杆可提供更大的奖励。动物必须选择是想要小的即时奖励还是更大的延迟奖励。通过这种方式，可以测量和量化冲动选择。该模型为我们提供了一个全新的临床相关视角，可以在临床前动物模型水平上评估潜在的治疗性抗成瘾、抗渴望、抗复发药物。在报告期间使用该模型，我们发现实验室大鼠将自己双峰地自我分类为具有高冲动选择的动物和其他具有低冲动选择的动物。我们进一步发现，在高冲动选择的动物中，可卡因会导致冲动性降低。相比之下，在低冲动选择的动物中，可卡因会产生更高冲动的转变。我们打算利用这种新的动物模型进一步探讨成瘾药物对冲动选择行为的影响。此外，在本报告期内，我们将酗酒动物模型引入我们的成瘾临床前动物模型系列中。在人类层面，暴饮暴食型吸毒行为往往是吸毒成瘾的特征。因此，我们增加了酗酒动物模型。在这项任务中，实验大鼠每天被允许喝水、近啤酒（不含乙醇）或啤酒（含2%乙醇）2小时。狂饮在操作上被定义为在初次饮酒后 2 小时内使血液乙醇水平达到至少 80 毫克/分升。我们的目的是使用这种新的动物模型来确定我们的任何假定的抗成瘾药物疗法是否可以在假定的治疗方向上改变酗酒。我们相信，这种新模型的加入为我们提供了另一个新的临床相关视角，可以在临床前动物模型水平上评估潜在的治疗性抗成瘾、抗渴望、抗复发药物。如果成功，我们打算调查其他成瘾药物的暴饮暴食。