Explorative Projects EP Project: The Role of Serotonin Receptor Genes in the Etiology of Gastrointestinal Disorders

Introduction Serotonin (5-hydroxytryptamine, 5-HT) controls a variety of physiological functions in the central and peripheral nervous system. Most of the serotonin can be found in the gastrointesinal tract (95%) besides its distribution in brain and blood cells (Gershon, 2003). Serotonin action is mediated by a multitude of 5-HT receptor subtypes. These subtypes can be divided into seven main classes (5-HT1R to 5-HT7R) based on their structural and functional features (Hoyer et al., 2002). Except for the 5-HT3 receptor, which is a ligand-gated ion channel, all serotonin receptors represent G-protein coupled binding proteins. The ion channel itself is an oligomeric complex composed of five subunits. During the last years two different human 5-HT3 receptor subunit genes, HTR3A and HTR3B, have been isolated (Miyake et al., 1995; Belelli et al., 1995; Davies et al., 1999).