THE IMPORTANCE OF 5-HYDROXYTRYPTAMINE RECEPTORS IN THE GUT

Most of the 5-hydroxytryptamine (5-HT) present in the adult human body is located in the gastrointestinal tract. The vast majority is contai ned in enteroendocrine cells, the rest exists mainly in myenteric inte rneurons separated from the mucosa by an intraenteric barrier. Physiol ogical studies suggest that 5-HT plays a vital role in mediating both sensory and reflex responses to gastrointestinal stimuli and, thus, th is transmitter is closely implicated in gut reactions. This review out lines some of the evidence for different 5-HT receptors, summarizes th e role of 5-HT in mediating gut sensitivity and motor activity, secret ion and more complex activities, such as emesis and diarrhoea and iden tifies the clinical role of drugs acting on 5-HT receptors in the trea tment of emesis, diarrhoea, the control of abdominal pain and discomfo rt and the rectification of gastrointestinal motility.