<prompt> Which of the following is true regarding 5-HT derivatives: March 2009Cisapride is selective 5-HT4 antagonistOndansetron is a 5-HT3 agonistCyproheptadine is 5-HT2A agonistSumatriptan action is agonistically 5-HT 1B1D receptor mediated  <response>: Ans. D: Sumatriptan action is agonistically 5-HT 1131D receptor mediated Cisapride and renzapride are selective 5-HT4 agonists. Ondansetron is a selective 5-HT3 antagonist which inhibits vomiting by blocking these receptors in brainstem as well as in gut wall. Cyproheptadine is 5-HT2A antagonist and has additional H1 antihistaminic, anticholinergic and sedative propeies. Sumatriptan and other triptan are selective 5-HT 1131D agonists, constricts cerebral blood vessels and has emerged as the most effective treatment of acute migraine attacks. 