Overview of Mechanisms for Coupling of Receptor-Agonist Interactions With Physiological Effects
There are many mechanisms by which receptor-ligand interactions are coupled to effector systems for the production of physiological effects. The intent is to provide a brief overview of the types of coupling mechanisms known to occur. Generally, with membrane-associated receptor systems a receptor-agonist interaction on one side of the membrane results in the production of a biochemical or biophysical change on the other side of the membrane. Ion channels may be directly coupled to receptors, which are probably true for the nicotinic acetyl choline receptor, or they may be indirectly coupled to receptors through intervening effector systems. Many membrane-associated receptor systems initiate their physiological effects through cyclic nucleotide-stimulated protein kinases or through direct stimulation of protein kinases without the requirement for the cyclic nucleotide intermediates. The adenylate cyclase receptor-linked systems have an additional feature, that of also being coupled to an inhibitory receptor.