title: Role of brain orexin in the pathophysiology of functional gastrointestinal disorders.
abstract: OBJECTIVE
  Orexins are neuropeptides that are localized in neurons within the lateral hypothalamic area and regulate feeding behavior. The lateral hypothalamic area plays an important role in not only feeding but the central regulation of other functions including gut physiology. Accumulating evidence have shown that orexins acts in the brain to regulate a wide variety of body functions including gastrointestinal functions.
  
  
  METHODS
  The purpose of this review is to summarize relevant findings on brain orexins and a digestive system, and discuss the pathophysiological roles of the peptides with special reference to functional gastrointestinal disorders.
  
  
  RESULTS
  Exogenously administered orexin or endogenously released orexin in the brain potently stimulates gastric acid secretion in pylorus-ligated conscious rats. The vagal cholinergic pathway is involved in the orexin-induced stimulation of acid secretion, suggesting that orexin-containing neurons in lateral hypothalamic area activates neurons in the dorsal motor nucleus in medulla oblongata, followed by increasing vagal outflow, thereby stimulating gastric acid secretion. In addition, brain orexin stimulates gastric motility, pancreatic secretion and induce gastroprotective action. On the other hand, brain orexin is involved in a number of physiological functions other than gut physiology, such as control of sleep/awake cycle and anti-depressive action in addition to increase in appetite.
  
  
  CONCLUSIONS
  From these evidence, we would like to make a hypothesis that decreased orexin signaling in the brain may play a role in the pathophysiology in a part of patients with functional gastrointestinal disorders who are frequently accompanied with appetite loss, sleep disturbance, depressive state and the inhibition of gut function.
authors: Department of General Medicine, Asahikawa Medical University, Asahikawa, Hokkaido, Japan. okumurat@asahikawa-med.ac.jp
authors: Toshikatsu
authors: T
authors: Okumura
authors: Tsukasa
authors: T
authors: Nozu
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism* / Q000503:physiopathology; D003863:Depression / Q000378:metabolism / Q000503:physiopathology; D005247:Feeding Behavior; D005744:Gastric Acid / Q000378:metabolism; D005767:Gastrointestinal Diseases / Q000378:metabolism* / Q000503:physiopathology / Q000523:psychology; D041981:Gastrointestinal Tract / Q000294:innervation / Q000378:metabolism / Q000503:physiopathology*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D009479:Neuropeptides / Q000378:metabolism*; D000068797:Orexins; D015398:Signal Transduction; D012890:Sleep
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D000068797:Orexins