With its particular emphasis on the constitutive activity of G-protein-coupled receptors (GPCRs)s, this book comprehensively discusses an important biological process that has not yet been covered in such depth in any other existing books on GPCRs. The international team of highly distinguished authors addresses in detail current models and concepts, to introduce medicinal chemists, physiologists, pharmacologists, and medical researchers into the advances in the understanding of GPCR activation and constitutive activity. In addition, the book provides an overview on methods of investigating constitutive GPCR activity. The text is well illustrated by selected experimental data and schemes.The chapters are all cross-referenced with each other and cover general mechanisms, methodological approaches and cover selected important GPCR systems, the consequences for drug action, including, side effects, and rational drug design for GPCR targets. The text is backed by abundant case studies and methodological advice for analysing GPCRs, covering selected pharmacologically relevant GPCR systems, the consequences for drug action, including unwanted side effects, and rational drug design for GPCR targets. It is a highly practical reference for researchers in academia and industry.