Serotonin (5-hydroxytryptamine, 5-HT) is an important signalling molecule in the human body. The 5-HT4 serotonin receptor, coupled to the G protein Gs, plays important physiological and pathophysiological roles in the heart, urinary bladder, gastrointestinal tract and the adrenal gland. Both 5-HT4 antagonists and agonists have been developed in the aim to treat diseases in these organs. 5-HT4 agonists might have beneficial effects in the ...