A comprehensive collection of readily reproducible methods for studying receptors in silico, in vitro, and in vivo. These cutting-edge techniques cover mining from curated databases, identifying novel receptors by high throughput screening, molecular methods to identify mRNA encoding receptors, radioligand binding assays and their analysis, quantitative autoradiography, and imaging receptors by positron emission tomography (PET). Highlights include phenotypic characterization of receptors in knockout mice, imaging receptors using green fluorescent protein and fluorescent resonance energy transfer, and quantitative analysis of receptor mRNA by TaqMan PCR. These book equips the researcher with techniques for exploring the unprecedented number of new receptor systems now emerging and the so-called "orphan" receptors whose activating ligand has not been identified.