HTR3A and Headache: The 5-HT3 antagonists exerts their antiemetic action by blocking the binding of serotonin to 5-HT3 receptors in the gut and the CTZ of area postrema which has got projections to the vomiting centre of lateral reticular formation of medulla oblongata.[35, 36] The side-effect profile of palonosetron seems to be more favorable as only 6.67% of patients experienced post-op headache in our study as compared 20% of such incidence in ondansetron group.