HTR3A and cancer: Interestingly, blocking the ligand-gated ion channel 5-HT3 receptor [13] may not only exert an antiemetic effect but also a putative intrinsic antiobsessive action, as suggested by the efficacy of ondansetron (a potent 5-HT3 antagonist used for chemotherapy-induced nausea) augmentation in treatment-resistant OCD [16,17], whereas olanzapine and mirtazapine 5-HT3 blockade has been considered for cancer chemotherapy-related nausea and cachexia (due to the H1 blockade) [18].