Bilsky Edward J, Giuvelis Denise, Osborn Melissa D, Dersch Christina M, Xu Heng, Rothman Richard B
Department of Biomedical Sciences, College of Osteopathic Medicine, University of New England, Biddeford, Maine, USA.
Methods Enzymol. 2010;484:413-43. doi: 10.1016/B978-0-12-381298-8.00021-6.
Constitutive (basal) signaling has been described and characterized for numerous G protein coupled receptors (GPCRs). The relevance of this activity to disease, drug discovery and development, and to clinical pharmacotherapy is just beginning to emerge. Opioid receptors were the first GPCR systems for which there was definitive evidence presented for constitutive activity, with numerous studies now published on the regulation of this activity (e.g., structure/activity of the receptor as it relates to basal activity, pharmacology of ligands that act as agonists, inverse agonists and "neutral antagonists," etc.). This chapter summarizes some of the methods used to characterize constitutive activity at the mu opioid receptor (MOR) in preclinical in vitro and in vivo model systems. This includes cell-based systems that are useful for higher throughput screening of novel ligands and for studying variables that can impact basal tone in a system. In vivo assays are also described in which constitutive activity is increased in response to acute or chronic opioid agonist exposure and where withdrawal is precipitated with antagonists that may function as inverse agonists or "neutral" antagonists. The methods described have inherent advantages and disadvantages that need to be considered in any drug discovery/development program. A brief discussion of progress toward understanding the clinical implications of MOR constitutive activity in the management of opioid addiction and chronic pain is also included in this chapter.
组成性（基础）信号传导已针对众多G蛋白偶联受体（GPCR）进行了描述和表征。这种活性与疾病、药物发现与开发以及临床药物治疗的相关性才刚刚开始显现。阿片受体是首个有确凿证据证明存在组成性活性的GPCR系统，目前已有大量关于该活性调节的研究发表（例如，受体的结构/活性与基础活性的关系、作为激动剂、反向激动剂和“中性拮抗剂”的配体的药理学等）。本章总结了在临床前体外和体内模型系统中用于表征μ阿片受体（MOR）组成性活性的一些方法。这包括基于细胞的系统，该系统可用于新型配体的高通量筛选以及研究可能影响系统基础张力的变量。还描述了体内试验，其中组成性活性会因急性或慢性阿片激动剂暴露而增加，并且使用可能作为反向激动剂或“中性”拮抗剂的拮抗剂引发戒断反应。所描述的方法具有固有的优点和缺点，在任何药物发现/开发计划中都需要加以考虑。本章还简要讨论了在理解MOR组成性活性在阿片类药物成瘾和慢性疼痛管理中的临床意义方面取得的进展。
