Radioligand binding is essentially a very simple technique, applicable to a wide range of preparations. It can of course be used to study many diff- ent types of receptors, but can also be adapted to investigate a variety of nonreceptor proteins, such as enzymes and uptake sites. The basic technique allows the affinity of drugs for the receptor of interest to be determined very easily, and the speed and precision of binding have led to its widespread use as a primary screen in drug discovery programs. It also allows receptor n- ber to be measured and the kinetics of the receptor-ligand interaction to be determined, parameters not readily accessible by any other means. Receptor distribution can be studied in great detail using the technique of autoradiog- phy; radioligand binding provides the most sensitive technique for dissecting allosteric interactions between ligands and receptors, and even between rec- tors and effector molecules, such as G proteins. Moreover, by allowing rec- tors to be identified in the absence of any measurable response, binding is a prerequisite for receptor solubilization and purification studies. It is even p- sible to measure ligand receptor interactions in vivo, using positron emission tomography and other powerful techniques. provides detailed experimental protocols for the measurement of binding to various receptor and nonreceptor sites in a range of preparations, including solubilized receptors, membrane preparations, whole cells, autoradiography, and PET and SPECT analysis in living human subjects.weiterlesen