Development of Antagonists for M5 Muscarinic Acetylcholine Receptor

描述(申请人提供)：药物滥用继续造成巨大的社会负担。尽管进行了密集的努力，但仍然缺乏针对药物依赖的有效药物治疗，这表明需要新的战略和目标。越来越多的证据支持我们的假设，即M5乙酰胆碱受体(MAChR)的选择性拮抗是治疗药物依赖的新靶点。大多数滥用药物的奖赏效应被认为是由中脑边缘多巴胺能通路分别从腹侧被盖区(VTA)和黑质致密部(SNC)投射到伏隔核(NAC)和纹状体。M5受体是定位于VTA和SNc的多巴胺能神经元的唯一亚型。向VTA或SNc内微量注射非选择性mAChR拮抗剂东莨菪碱可显著减少NAc或纹状体的DA释放。尽管目前还没有选择性的M5受体拮抗剂，但使用缺乏功能性M5受体的小鼠进行的行为研究表明，在注射吗啡和可卡因后，奖赏和戒断反应减少，可卡因自身给药的速度也降低。这些结果表明，M5受体在调节可卡因和阿片成瘾方面发挥了作用。此外，东莨菪碱与可卡因联合给药可减少恒河猴对可卡因的自身给药，临床研究表明东莨菪碱对海洛因成瘾者脱毒有效。我们推测东莨菪碱的作用是由于M5受体的拮抗作用，但不能排除其他亚型的参与。到目前为止，M5mAChR的生理和药理作用仍然不清楚，缺乏亚型选择性的M5配体阻碍了研究。这项应用的目标是发现有效和选择性的M5受体拮抗剂，在我们的长期目标中，可以开发成药物依赖的药物治疗。我们期望在这项研究项目中开发的化合物也将作为药理学工具用于研究M5受体的生理功能。新的化合物将在文献报道的低选择性和低效性M5拮抗剂的基础上设计和合成。合成的化合物将被鉴定为在表达单个人M受体亚型的重组中国仓鼠卵巢(CHO-K1)细胞中的受体结合亲和力，在表达hM5受体的CHO细胞中抑制卡巴胆碱诱导的磷脂酰肌醇(PI)水解的能力，以及通过抑制奥曲莫林从超融合大鼠纹状体切片中释放多巴胺的能力(功能分析)。公共卫生相关性：这些研究将开创开发选择性M5受体拮抗剂的先河，这些拮抗剂有可能成为药物滥用的有效治疗方法。

DESCRIPTION (provided by applicant): Drug abuse continues to cause great societal burden. Despite intensive efforts, effective pharmacotherapeutic treatments for drug dependence are still lacking, indicating new strategies and targets are needed. A growing body of evidence supports our hypothesis that selective antagonism at the M5 muscarinic acetylcholine receptor (mAChR) represents a novel target for the treatment of drug dependence. The rewarding effects of most drugs of abuse are believed to be mediated by the mesolimbic dopaminergic pathway projecting from the ventral tegmental area (VTA) and substantia nigra pars compacta (SNc) to the nucleus accumbens (NAc) and striatum, respectively. The M5 receptor is the only subtype localized on dopaminergic neurons of the VTA and SNc. Microinfusion of the non-selective mAChR antagonist scopolamine into the VTA or SNc substantially reduces DA release in NAc or striatum, respectively. Although there are no selective M5 receptor antagonists currently available, behavioral studies using mice lacking functional M5 receptors have shown a reduction in reward and withdrawal responses following morphine and cocaine administration, and also a reduction in the rate of cocaine self-administration. These results show a role of the M5 receptor in modulating cocaine and opiate addiction. Furthermore, co-administration of scopolamine with cocaine reduces self-administration of cocaine by rhesus monkeys, and scopolamine has been shown to be effective for detoxification of heroin addicts in clinical studies. We reasoned that the effectiveness of scopolamine is due to antagonism of the M5 receptor; however, the involvement of other subtypes can not be ruled out. To date, the physiological and pharmacological roles of the M5 mAChR are still obscure and research has been hampered by the lack of subtype-selective M5 ligands. The objective of this application is to discover potent and selective M5 receptor antagonists, which, in our long-term goal, can be developed into medical treatments for drug dependence. We expect that compounds developed in this research project will also serve as pharmacological tools useful for studying physiological functions of the M5 receptor. New compounds will be designed and synthesized based on the structural scaffold of literature reports on low selectivity and low potency M5 antagonists. Compounds synthesized will be characterized for receptor binding affinities in recombinant Chinese hamster ovarian (CHO- K1) cells expressing the individual human muscarinic receptor subtypes, ability to inhibit carbachol-induced phosphatidylinositol (PI) hydrolysis in CHO cells expressing hM5 receptors and by inhibition of oxotremorine- evoked dopamine release from superfused rat striatal slices (functional assay). PUBLIC HEALTH RELEVANCE: These studies will pioneer the development of selective M5 receptor antagonists which have potential as efficacious treatments for drugs of abuse.