Neuromedin U is necessary for normal gastrointestinal motility and is regulated by serotonin.

Neuromedin U (NMU) was originally isolated from porcine spinal cord and shown to be distributed in numerous tissues, including the gastrointestinal tract. However, little is known about the role of NMU in the regulation of gastrointestinal functions. We established a radioimmunoassay system that is exceptionally specific for mouse NMU and found high NMU content in the gastrointestinal tract, particularly in the Auerbach's and Meissner's plexi, suggesting a possible role of NMU in gastrointestinal motility. NMU promoted small intestinal transit, and NMU deficiency resulted in lowered intestinal motility rate and diminished the effect of serotonin-induced defecation and diarrhea. These results indicate that NMU promotes intestinal transit and maintains intestinal homeostasis.