3 Drug Receptor Interactions

Abstract

This chapter reviews that the concept of a receptor proves to be remarkably elusive, considering the central position it occupies in the theory of pharmacology. A receptor is considered as the component of a cell with which a drug combines to initiate a response. It is suggested that the receptor has a complementary structure to the drug and that, owing to the weakness of the forces binding the drug to the receptor, a very close fit between the two is needed for firm binding. Owing to the cooperative and complementary nature of these binding forces, any deviation from the optimal structure, for example by the substitution of a bulky group for a small one, by rearranging the constituent groups of a molecule in space by inversion at an asymmetric centre, or by altering the direction of a dipole within the molecule, causes a profound alteration in the stability of the drug-receptor complex. The chapter focuses on few general ideas: (1) the factors influencing the size and shape of drug molecules in solution, (2) the nature and properties of some of the components of cellular systems that may be responsible for the specific combination of drugs, (3) the forces that may bind drug molecules to these receptor substances, and (4) the possible effects of drug combination on the structure and properties of cellular components.