Saturation Assays of Radioligand Binding to Receptors and Their Allosteric Modulatory Sites

AbstractThe protocols in this unit describe methods for measuring radioligand binding to sites on the GABA‐A receptor complex. This system was chosen because of the fundamental role of GABA‐A receptors in central nervous system function and the presence of multiple binding sites on one supramolecular complex. However, these basic techniques can be used to analyze ligand binding to a wide variety of intracellular and extracellular sites associated with ion channels, transporters, or G proteins with relatively simple modifications of the protocols (e.g., tissue preparation, buffers, assay termination techniques, incubation times, and temperatures). A saturation assay is presented to examine ligand binding to the benzodiazepine site on the GABA‐A receptor, while a second protocol uses a similar technique to examine the binding site for GABA in this complex.