Development of Antagonists for M5 Muscarinic Acetylcholine Receptor

描述（由申请人提供）：药物滥用继续造成巨大的社会负担。尽管作出了大量努力，但仍然缺乏有效的药物依赖治疗，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，在M5毒蕈碱乙酰胆碱受体（mAChR）的选择性拮抗作用是一种新的药物依赖治疗的目标。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介导的，该通路分别从腹侧被盖区（VTA）和黑质背侧部（SNc）投射到丘脑核（NAc）和纹状体。M5受体是腹侧被盖区和黑质腹侧被盖区多巴胺能神经元上唯一的受体亚型。将非选择性mAChR拮抗剂东莨菪碱微输注到VTA或SNc中分别显著降低NAc或纹状体中的DA释放。虽然目前没有选择性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显示，吗啡和可卡因给药后奖赏和戒断反应减少，可卡因自我给药率也降低。这些结果显示了M5受体在调节可卡因和阿片成瘾中的作用。此外，东莨菪碱与可卡因的共同给药减少了恒河猴对可卡因的自我给药，并且东莨菪碱在临床研究中已被证明对海洛因成瘾者的解毒有效。我们推断东莨菪碱的有效性是由于M5受体的拮抗作用;然而，不能排除其他亚型的参与。迄今为止，M5 mAChR的生理学和药理学作用仍然不清楚，并且由于缺乏亚型选择性M5配体而阻碍了研究。本申请的目的是发现有效的和选择性的M5受体拮抗剂，在我们的长期目标中，其可以被开发成药物依赖的医学治疗。我们期望在本研究项目中开发的化合物也将作为用于研究M5受体生理功能的药理学工具。基于低选择性和低效力的M5拮抗剂的文献报道的结构支架，将设计和合成新的化合物。将表征合成的化合物在表达单个人毒蕈碱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hM 5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氧震颤素诱发的多巴胺从灌流的大鼠纹状体切片释放（功能测定）来表征。公共卫生相关性：这些研究将开创选择性M5受体拮抗剂的发展，这些拮抗剂有可能作为药物滥用的有效治疗。

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.