Glutamatergic compounds for treating drug addiction: Preclinical models

用于治疗药物成瘾的谷氨酸化合物：临床前模型

• 批准号: 8336448
• 负责人: Eliot Gardner
• 金额: $ 34.68万
• 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/8336448
• 关键词: Addictive Behavior; Agonist; Animal Model; Attenuated; Behavior; Biochemical; Biological Assay; Brain; Chemicals; Chronic; Cocaine; Cocaine Dependence; Corpus striatum structure; Cues; Data; Development; Dopamine; Dorsal; Dose; Drug Addiction; Electrical Stimulation of the Brain; Enzymes; Exposure to; Globus Pallidus; Glutamate Carboxypeptidase II; Glutamate Receptor; Glutamates; Goals; Habits; High Pressure Liquid Chromatography; Immunoblotting; Infusion procedures; Injection of therapeutic agent; Intravenous; Laboratory Animals; Laboratory Rat; Measures; Mediating; Metabotropic Glutamate Receptors; Methods; Microdialysis; Microinjections; N-acetylaspartylglutamate; Neuropeptides; Neurotransmitters; Nucleus Accumbens; Perfusion; Pharmaceutical Preparations; Polymerase Chain Reaction; Pre-Clinical Model; Prosencephalon; Proteins; Psychological reinforcement; RNA; Rattus; Relapse; Reporting; Research; Research Project Grants; Resistance; Reverse Transcription; Rewards; Role; Sampling; Self Administration; Stress; System; Techniques; Tetrodotoxin; Western Blotting; Work; addiction; craving; drug seeking behavior; extracellular; gamma-Aminobutyric Acid; glutamate receptor subunit 3; in vivo; inhibitor/antagonist; interest; metabotropic glutamate receptor 2; metabotropic glutamate receptor 3; metabotropic glutamate receptor 7; methylserine phosphate; neurotransmission; pinacolyl methylphosphonic acid; pre-clinical; preference; presynaptic; prevent; protective effect; pyridine; receptor; research study

During the reporting period, considerable progress was made on this research project. Research studies have previously shown that chronic or repeated cocaine administration produces long-term alterations in glutamate neurotransmission in the brain. We previously studied glutamatergic involvement in addiction by studying mGluR5 glutamate receptor antagonism in animal models relating to addiction. We found that blockade of the mGluR5 glutamate brain receptor by the selective, potent, and systemically-active mGluR5 receptor antagonist MPEP (2-methyl-6-(phenylethynyl)-pyridine) inhibits cocaine self-administration under fixed-ratio reinforcement conditions and inhibits cocaine self-administration under progressive-ratio reinforcement conditions in laboratory rats (i.e., significantly reduces the amount of work that laboratory rats are willing to expend to receive intravenous cocaine infusions). We further found that blockade of the mGluR5 glutamate receptor by MPEP significantly inhibits relapse to drug-seeking behavior triggered by cocaine, but not relapse to drug-seeking behavior triggered by either stress or environmental cues previously paired with drug-taking behavior. By using in vivo brain microdialysis methods, we further found that MPEP has no effect on extracellular levels of the neurotransmitter dopamine in the nucleus accumbens of the limbic forebrain in either drug-naive or cocaine-extinguished rats, suggesting a dopamine-independent mechanism underlying MPEP's actions. In contrast, MPEP (administered either systemically or locally into the nucleus accumbens) elevates extracellular glutamate. Furthermore, MPEP dose-dependently inhibited cocaine-induced increases in nucleus accumbens extracellular glutamate in both drug-naive and cocaine-extinguished rats. These data suggested that alterations in nucleus accumbens glutamate may underlie MPEP's actions on cocaine-induced reward and cocaine-triggered relapse to drug-seeking behavior, and confirmed that brain glutamate neurotransmission constitutes an attractive target for potential anti-addiction, anti-craving, anti-relapse medications. During the present reporting period, we studied NAALADase inhibition in animal models relating to addiction. NAALADase (N-acetylated-alpha-linked-acidic dipeptidase; glutamate carboxypeptidase II) is a brain enzyme which hydrolyzes the endogenous brain neuropeptide NAAG (N-acetyl-aspartyl-glutamate) to glutamate and NAA (N-acetyl-aspartate). NAAG is an endogenous mGluR3 glutamate receptor agonist, which inhibits presynaptic glutamate release. Therefore, studies of NAALADase inhibitors in preclinical animal models relating to addiction are of interest in the search for clinically useful pharmacotherapeutic agents for the treatment of addiction, craving, and relapse. Consequently, we studied the effects of 4 NAALADase inhibitors - 2-PMPA, GPI-5693, GPI-16476, and GPI-16477 - in animal models relating to addiction. We found that all 4 NAALADase inhibitors had no effect on intravenous cocaine self-administration under fixed-ratio reinforcement conditions, but significantly inhibited cocaine-triggered relapse to cocaine-seeking behavior in laboratory rats who had been pharmacologically detoxified and behaviorally extinguished from their prior intravenous cocaine-taking habits. This protective effect against cocaine-triggered relapse to drug-seeking behavior was blocked by intracerebral microinjections of LY341495, a selective mGluR2/3 receptor antagonist, directly into the nucleus accumbens in the brain. This implicates the mGluR2/3 glutamate receptor of the brain in this anti-addiction action. We further found that the NAALADase inhibitor 2-PMPA significantly inhibits cocaine self-administration under progressive-ratio reinforcement conditions (i.e., significantly reduces the amount of work that laboratory rats are willing to expend to receive intravenous cocaine infusions). We further found tthat 2-PMPA and NAAG significantly inhibit cocaine-enhanced brain-stimulation reward and intravenous cocaine self-administration in laboratory rats, and that 2-PMPA attenuates coaine-enhanced dopamine in the nucleus accumbens - an effect that was prevented by LY341495, implicating the involvement of mGluR2/3 rceptors in these effects. We additionally studied the effects of AMN082, a selective mGluR7 agonist, on extracellular dopamine, gamma-aminobutyric acid (GABA), and glutamate in the nucleus accumbens of the brain as measured by in vivo brain microdialysis. We found that systemic or intra-accumbens administration of AMN082 dose-dependently lowered extracellular GABA, increased extracellular glutamate, and had no effect on extracellular nucleus accumbens dopamine levels. We found that these effects were blocked by MSOP, a group III-selective mGluR antagonist. Intra-accumbens perfusion of tetrodotoxin (TTX) blocked the AMN082-induced increases in glutamate, but failed to block the AMN082-induced reduction in GABA, suggesting vesicular and non-vesicular GABA origins for these effects, respectively. We also found that intra-accumbens perfusion of the selective GABA-B receptor antagonist 2-hydroxysaclofen not only abolished the enhanced extracellular glutamate produced by AMN082, but actually decreased extracellular glutamate in a TTX-resistant manner. Further, during the present reporting period we found that systemically-administered AMN082 dose-dependently inhibits cocaine-triggered reinstatement of drug-seeking behavior. Intracerebral micro-injections of AMN082 into the nucleus accumbens or ventral pallidum, but not into the dorsal striatum, also inhibited cocaine-triggered relapse to drug-seeking behavior, an effect that was blocked by local intracerebral co-administration of MMPIP, a selective mGluR7 receptor antagonist. Pre-treatment with AMN082 dose-dependently blocked both cocaine-enhanced nucleus accumbens glutamate and cocaine-triggered relapse to drug-seeking behavior, an effect that was blocked by MMPIP or the selective mGluR2/3 receptor antgaonist LY341497. These findings suggest that mGluR7 activation inhibits cocaine-triggered relapse to drug-seeking behavior by a glutamate-mGluR2/3 mechanism in the nucleus accumbens. Such findings suggest a potential utility for mGluR7 receptor agonists for the treatment of cocaine addiction. In all, these findings suggest that the glutamate neurotransmitter system in the brain may be an appropriate target-of-action for the development of potential anti-addiction, anti-craving, and anti-relapse medications.

在本报告所述期间，这项研究项目取得了相当大的进展。先前的研究表明，长期或反复服用可卡因会对大脑中的谷氨酸神经传递产生长期的改变。我们之前通过研究与成瘾相关的动物模型中的mGluR5谷氨酸受体拮抗剂来研究谷氨酸能在成瘾中的作用。我们发现，mGluR5受体拮抗剂MPEP（2-甲基-6-（苯乙基）吡啶）阻断mGluR5谷氨酸脑受体抑制固定比例强化条件下的可卡因自我给药，并抑制实验室大鼠(即：大大减少了实验鼠接受静脉注射可卡因的工作量)。我们进一步发现，MPEP阻断mGluR5谷氨酸受体可显著抑制可卡因引发的寻求药物行为的复发，但对先前与吸毒行为相关联的压力或环境线索引发的寻求药物行为的复发不起作用。通过体内脑微透析方法，我们进一步发现MPEP对未用药或可卡因灭活大鼠边缘前脑伏隔核神经递质多巴胺的细胞外水平没有影响，这表明MPEP的作用机制与多巴胺无关。相反，MPEP（全身或局部注入伏隔核）可提高细胞外谷氨酸。此外，MPEP剂量依赖性地抑制可卡因诱导的伏隔核细胞外谷氨酸的增加。这些数据表明，伏隔核谷氨酸的改变可能是MPEP对可卡因诱导的奖励和可卡因引发的药物寻求行为复发的作用的基础，并证实脑谷氨酸神经传递是潜在的抗成瘾、抗渴望、抗复发药物的一个有吸引力的靶点。在本报告期间，我们研究了与成瘾有关的动物模型中的NAALADase抑制。NAALADase （n -乙酰化- α -连接-酸性二肽酶；谷氨酸羧肽酶II）是一种将内源性脑神经肽NAAG （n -乙酰-天冬氨酸-谷氨酸）水解为谷氨酸和NAA （n -乙酰-天冬氨酸）的脑酶。NAAG是一种内源性mGluR3谷氨酸受体激动剂，可抑制突触前谷氨酸释放。因此，在与成瘾相关的临床前动物模型中研究NAALADase抑制剂，对于寻找治疗成瘾、渴望和复发的临床有用药物治疗药物具有重要意义。因此，我们研究了4种NAALADase抑制剂- 2-PMPA， GPI-5693， GPI-16476和GPI-16477 -在与成瘾相关的动物模型中的作用。我们发现，在固定比例强化条件下，所有4种NAALADase抑制剂对静脉注射可卡因自我给药没有影响，但在药理学上解毒和行为上消失的实验室大鼠中，它们明显抑制可卡因引发的可卡因寻求行为的复发。这种对可卡因引发的药物寻求行为复发的保护作用被直接注射到大脑伏隔核的LY341495（一种选择性mGluR2/3受体拮抗剂）阻断。这暗示大脑的mGluR2/3谷氨酸受体参与了这种抗成瘾作用。我们进一步发现，在递进比例强化条件下，NAALADase抑制剂2-PMPA显著抑制可卡因自我给药（即显著减少实验室大鼠为接受静脉注射可卡因而愿意付出的工作量）。我们进一步发现，在实验室大鼠中，2-PMPA和NAAG显著抑制可卡因增强的脑刺激奖励和静脉可卡因自我给药，并且2-PMPA减弱了伏隔核中可卡因增强的多巴胺——LY341495阻止了这一作用，暗示mGluR2/3受体参与了这些作用。我们还研究了选择性mGluR7激动剂AMN082对大脑伏隔核细胞外多巴胺、γ -氨基丁酸（GABA）和谷氨酸的影响，这是通过体内脑微透析测量的。我们发现全身或伏隔核内给予AMN082剂量依赖性地降低细胞外GABA，增加细胞外谷氨酸，而对细胞外伏隔核多巴胺水平没有影响。我们发现这些作用被MSOP阻断，MSOP是一种iii组选择性mGluR拮抗剂。伏隔区内灌注河豚毒素（TTX）阻断了amn082诱导的谷氨酸增加，但未能阻断amn082诱导的GABA减少，提示这些作用分别来自水疱和非水疱GABA。我们还发现，选择性GABA-B受体拮抗剂2-羟氯芬在伏隔核内灌注不仅消除了AMN082产生的增强的细胞外谷氨酸，而且实际上以ttx耐药的方式降低了细胞外谷氨酸。此外，在本报告期间，我们发现系统给予AMN082剂量依赖性抑制可卡因引发的药物寻求行为的恢复。将AMN082脑内微注射到伏隔核或腹侧苍白体，但不注射到背侧纹状体，也能抑制可卡因引发的药物寻求行为的复发，这一作用被局部脑内联合给药MMPIP（一种选择性mGluR7受体拮抗剂）阻断。AMN082剂量依赖性地阻断了可卡因增强的伏隔核谷氨酸和可卡因引发的药物寻求行为的复发，这一作用可被MMPIP或选择性mGluR2/3受体拮抗剂LY341497阻断。这些发现表明mGluR7的激活通过谷氨酸- mglur2 /3机制抑制伏隔核中可卡因引发的药物寻求行为的复发。这些发现表明mGluR7受体激动剂在治疗可卡因成瘾方面具有潜在的效用。总之，这些发现表明，大脑中的谷氨酸神经递质系统可能是开发潜在的抗成瘾、抗渴望和抗复发药物的合适靶点。