Introduction To Receptors
The primary theoretical basis for modern pharmacology is the receptor concept. This holds those drugs, hormones, neurotransmitters, toxins, and other biologically active substances (collectively referred to as ligands) exert their actions by way of interaction with receptors. Receptors are usually proteins and they are often incorporated into membranes or associated with membranes. Receptors also may be associated with structures other than membranes, such as DNA, or they can be “soluble”. In addition to a precise fit, binding of a ligand to its receptor is also the result of attractive forces between the receptor and the ligand. Much like the north pole of a magnet attracting the south pole of another magnet, the receptor and ligand attract one another. When an agonist interacts with its receptor the stimulation of the receptor initiates a sequence of events that results in a physiological response. In the example of the nicotinic acetyl choline receptor, muscle contraction is the physiological effect produced by receptor stimulation.