Receptors

Receptors

INTRODUCTION

One of the basic tenets of pharmacology is that drug molecules exert some chemical influence on one or more constituents of the cells to produce a pharmacological response. Of course, the molecules in an organism are vastly outnumbered, but the drug molecules should be merely distributed at random to get a chance to interact with any particular class of proteins. The biological activity is studied by understanding the nature of binding sites and the mechanism by which the association of drug molecules take place. There are four primary target regulator proteins that are commonly involved in the drug interactions to produce pharmacological actions. They are enzymes, carrier molecules, ion channels, and  receptors.

The term receptor or a receptive substance was used to denote a small region of macromolecule, which may be an isolable enzyme, a structural and functional compound of a cell membrane, or a specific intracellular substance, such as a protein or a nucleic acid. Occupation of a receptor by a drug molecule may or may not result in the activation of the receptor. Activations result in tissue responses. Binding and activation represent the two steps in the generation of receptor-mediated response by an agonist. If a drug binds to a receptor causing activation, and thereby prevents the agonist from binding, it is termed as a receptor antagonist, whereas the tendency for it once bound to activate the receptor is denoted by efficacy. Drugs with intermediate levels of efficacy produces submaximal response even at 100% receptor occupation are known as partial agonist. Those, which produce maximum response after 100% receptor occupation, are called full agonist.