5-HT3 receptors and the therapeutic potential of 5-HT3 receptor antagonists.

5-HT3 receptors have been the focus of much research during the last decade. They are characterised by being located on neurones both peripherally and centrally; 5-HT3 agonists cause a rapid depolarisation of the membrane potential which results from the opening of cation channels; the 5-HT3 response rapidly desensitizes. 5-HT3 receptors appear to have a modulatory role on other neurotransmitters. The identification of selective agonists and antagonists for this receptor type has allowed the discovery of several important new therapeutic applications. The use of 5-HT3 receptor antagonists in psychoactive illnesses is being explored clinically. In addition, ondansetron, a selective 5-HT3 receptor antagonist, is already being used to prevent the severe nausea and vomiting caused by cancer chemotherapy and radiotherapy. The pharmacological properties of 5-HT3 antagonists are discussed in this chapter.