<prompt> Antiemetic action is produced through:Decreased CTZ stimulationH1 agonistic actionD1 antagonistic actionOlfactory apparatus stimulation  <response>: Mechanism of action of antiemetic drugs are: Anticholinergic e.g hyoscine H1 antihistaminics e.g promethazine,diphenyhydramine,cyclizine. 5-HT3 antagonists e.g ondansetrone,granisetron Prokinetics. 5HT4 agonists e.g cisapride. Motilin agonist e.g erythromycin. CTZ contains histamine dopamine,cholinergic,opioid and serotonin receptors.antiemetic acts by inhibiting the receptors at CTZ. ref KDT 6e p643 