Pharmacological Receptors in the Prostate

Abstract

It is generally accepted that autonomic control of smooth muscle is mediated by chemical sub-stances—neurotransmitters—liberated at the nerve endings. In the case of the postganglionic sympathetic nerve fibers, the neurotransmitter is norepinephrine, and in the case of the postganglionic parasympathetic nerves, as well as the pre-ganglionic nerves of both types, the neurotransmitter is acetylcholine. In each case, in order for the neurotransmitter to produce an effect on the target organ, e.g., smooth muscle, there must be suitable sites on the cell membrane that can accept that particular chemical substance. Such sites, presumably consisting of suitable molecular configurations, are known as receptors. The neurotransmitter combines with the appropriate receptor, producing a characteristic response, and is known as an agonist. Other compounds with a similar specific effect are likewise known as agonists. It should be clear that if a given type of receptor is not present in the tissue, the corresponding agonist will not produce any effect on that tissue. Another group of substances also unite with the receptors but without producing a biological effect. By virtue of the fact that these substances occupy the sites of the receptors, they block the access of the agonists, and are thus known as “blockers.”