PHARMACOLOGY OF SEROTONIN AS RELATED TO ANESTHESIA

Serotonin (5-hydroxytryptamine) is an important biogenic amine that fu lfills the role of neurotransmitter and neuromodulator. It has been a focus of interest during the last decade. Its diversity of pharmacolog ic actions is related to a wide variety of receptors and effector mech anisms. Seven serotonin receptor families have been identified thus fa r. They are genetically different transmembrane proteins composed of s everal hundred amino acids. The majority of these are G-protein-couple d, except the 5-HT3 receptors, which are directly ligand gated to fast ion channels. Serotonin is widely distributed in the body within the central and peripheral nervous systems, smooth muscles, and platelets, in particular. Consequently, its effects manifest mainly in these org ans and influence a wide variety of neural, vascular, smooth muscle, a nd platelet functions. (Melatonin, a physiologically active metabolite of serotonin, is also instrumental in affecting many neural and hormo nal functions.) Several selective agonists and particularly many selec tive antagonists have been developed for serotonin, which helped the s erotonin receptor subtype classification. Some of these drugs are also used therapeutically in the treatment of migraine (eg, sumatriptan, w hich is a 5-HT1 receptor agonist), vascular disorders (5-HT2 antagonis ts), and nausea and vomiting (5-HT3 antagonists, eg, dolasetron, grani setron, ondansetron, and tropisetron), and have been investigated in g astrointestinal motility disorders (5-HT4 antagonists) and behavioral psychopathologies (5-HT1 agonists and 5-HT2-4 antagonists). Serotonin reuptake inhibitors are of particular clinical importance in the treat ment of psychological illnesses. Future use of these drugs is also env isioned in the treatment of certain types of pain syndromes. Awareness of the serotonergic drugs and the recognition of possible drug intera ctions among drugs that influence serotonergic mechanisms in humans ar e becoming increasingly important in the practice of anesthesiology.