Development of Antagonists for M5 Muscarinic Acetylcholine Receptor

描述（由申请人提供）：滥用药物继续造成巨大的社会负担。尽管付出了巨大的努力，但有效的药物治疗药物依赖仍然缺乏，这表明需要新的策略和靶点。越来越多的证据支持我们的假设，即M5毒蕈碱乙酰胆碱受体（mAChR）的选择性拮抗是治疗药物依赖的新靶点。大多数药物滥用的奖赏效应被认为是由分别从腹侧被盖区（VTA）和黑质致密部（SNc）投射到伏隔核（NAc）和纹状体的中边缘多巴胺能通路介导的。M5受体是唯一定位于VTA和SNc多巴胺能神经元的亚型。将非选择性mAChR拮抗剂东莨菪碱微量注入VTA或SNc，分别显著减少NAc或纹状体中DA的释放。虽然目前还没有选择性的M5受体拮抗剂，但对缺乏功能性M5受体的小鼠进行的行为研究表明，吗啡和可卡因给药后，小鼠的奖励和戒断反应减少，可卡因自我给药率也降低。这些结果表明M5受体在调节可卡因和鸦片成瘾中的作用。此外，东莨菪碱与可卡因的共同施用减少了恒河猴对可卡因的自我施用，并且在临床研究中已证明东莨菪碱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对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的生理和药理作用仍然不清楚，并且由于缺乏亚型选择性的M5配体，研究受到阻碍。这项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，可以开发成药物依赖的医学治疗方法。我们期望本研究项目开发的化合物也可以作为研究M5受体生理功能的药理学工具。以文献报道的低选择性、低效M5拮抗剂为结构支架，设计和合成新的化合物。合成的化合物将在表达个体毒毒碱受体亚型的重组中国鼠卵巢（CHO- K1）细胞中进行受体结合亲和力的表征，抑制表达hM5受体的CHO细胞中碳水化合物诱导的磷脂酰肌醇（PI）水解的能力，以及抑制过量使用的大鼠纹状体切片中氧tremorine诱发的多巴胺释放（功能测定）。公共卫生相关性：这些研究将开拓选择性M5受体拮抗剂的开发，有可能成为滥用药物的有效治疗方法。

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.