With contributions from international experts in the fields of pharmacology, neuroscience, and biochemistry, this text provides an in-depth exploration of GPCRs. Coverage includes the screening of ligands for GPCRs, physiological and molecular characterizations of GPCRs, and structures of GPCRs and their ligands. The book explores current research issues in the post-genome era, particularly the identification of endogenous ligands that may lead to finding new hormones or neurotransmitters. It also discusses the determination of the tertiary structure of GPCRs, useful for understanding GPCR interactions and for the theoretical modeling of drugs.