| [ Summary ] |
About 80 to 90% of 5-hydroxytryptamine(5-HT) is localized in the gastrointestinal tract. Its function has attracted attention in the regulation of the digestive organs. In addition, 5-HT-containing nerve fibers have been found to exist and play a part as one of the neurotrasmitters in the enteric nervous system. Most 5-HT receptor subtypes are classified as the G-protein-coupled type, while 5-HT3 receptors belong to the ligand-gated ion channel type. At least six subtypes of 5-HT receptors have been shown to exist in the gastroin-testinal tract. Clinically, two types of agents have recently been developed and are very effective;i.e., 5-HT3 antagonists and 5-HT4 agonists. The former has been used as an anti-emetic during the chemotherapy, and the latter has been shown to improve gastrointestinal motility. New drugs have been shown to be very specific to this receptor. |