Gq-mediated calcium mobilization activity was determined using HEK293 cells stably expressing corresponding 5-HT2 subtypes on FLIPRTETRA. Normalized results (relative fluorescence unit in fold of basal, basal was set as 0% and 5-HT Emax was set as 100%) represented mean values ± SEM from 2 independent assays, each performed in quadruplicate, and were analyzed in Prism. In antagonist activity assays, the reference agonist (5-HT) was used at a final concentration of 10 nM and was set as 0% inhibition and basal was set as 100% inhibition. Panels A–C represent dose-response curves to 5-HT, W-15 and W-18 at 5-HT2A (A), 5-HT2B (B), or 5-HT2C (C) receptors. Panels D–F shows the antagonist activity of W-15 and W-18 at 5-HT2A (D), 5-HT2B (E), or 5-HT2C (F) receptors.