<prompt> Ondansetron acts by:Action on CTZ5-HT3 antagonismD1 and D2 receptor antagonismIncreasing GIT motility  <response>: Ondansetron blocks the depolarizing action of serotonin through 5-HT3 receptors on vagal afferents in the gut as well as in NTS and CTZ. It donot block dopamine receptors or ACH receptors. ref KDT 6e p646 