Among the following 5HT3 antagonist is -

Ans. is 'b' i.e.. OndansetronSerotonin Receptors5 HT 15 HT 2A/2C5 HT 35 HT 4Presynapric autoreceptorCause constriction of cranial vesselsResponsible for most of the direct actions of serotoninIonotropic receptor (all other 5 HT receptors are G-protein coupled receptors).Present in GIT responsible for the increase in peristalsis.Modulates the release of serotoninAgonists at this receptor (sumatriptan, naratriptan) are useful for the treatment of acute migraine atackKetanserin and ritanserin (antagonists) are useful as anti hypertensive agentsMediates most of the reflex and indirect actions of serotonin.Agonists (cisapride, mosapride, renzapride, tegaserod) are useful in the treatment of GERDPartial agonists of this receptor (buspirone. ipsapirone, gespirone) are useful as antianxiety drugs Clozapine and risperidone are atypical antipsychotic agents that act through antagonistic activity at this receptor.Stimulation is responsible for vomiting induced by anticancer drugs. Antagonists like ondansetron, granisetron and tropisetron are the agents of choice for chemotherapy induced vomiting.