Receptor Binding Techniques

1 Overview of Ligand-Receptor Binding Techniques Michelle Qume 1. Introduction The aim of this chapter is to give a general overview of techniques employed in the process of ligand-receptor binding. The theoretical aspectsof the ligandreceptor interactions and mathematical aspectsof binding are not detailed here. These are considered m Chapter 9, and there are also very readable chapters in refs. I and 2. The techniques referred to use radioligands in the study of the central nervous system, but many are apphcable to work outside this field, for example, GABA binding in the periphery (3) as well as nonradioligands such as fluorescent and enzyme-linked antibodies. The first question to be asked is, “What do I want to measure?’ This is a function of the following questions. “What receptor?’ “Where is the receptor?” “What ligand? ” “What sort of results am I interested m?” “Do I have the time for techniques requiring exposure times of weeks, or do I need an answer now?’ Other queries regarding the amount of tissue available, and so forth, are all components of the decision of which technique to use. 2. Basic Radiollgand Binding Theory The basic theory behind radioligand binding is that receptor [R] plus ligand [L] bind reversibly to produce a bound receptor-ligand complex [RL] with free ligand remaining. It is this complex that is measured with radiohgand binding, whether in simple total and nonspecific analysis or in the more complicated saturation and competition binding assays.There are many papers detailing the mathematical models mvolved in this and other more complicated processes, but they are beyond this chapter. For further details, the reader is referred to Chapter 9. Fro