HTR4 and irritable bowel syndrome: Although 5-HT3 antagonists, 5-HT4 agonists, antispasmodics and alosetron have been shown to be useful for the treatment of IBS,6 regrettably, some drugs, such as guanylate cyclase-C agonists and loperamide, have been proven to be inadequate for relieving symptoms.6 7 Similarly, some psychological therapies, such as hypnotherapy, relaxation therapy and cognitive–behavioural therapy, have been proven to be effective treatments for IBS.8 Even when these available treatments are used, symptoms can persist for more than 12 months in some patients with IBS.