Department of General Medicine, Asahikawa Medical University, Asahikawa, Hokkaido, Japan.
J Gastroenterol Hepatol. 2011 Apr;26 Suppl 3:61-6. doi: 10.1111/j.1440-1746.2011.06626.x.
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.
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.
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.
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.
食欲素是一种神经肽，位于下丘脑外侧区的神经元内，调节摄食行为。下丘脑外侧区不仅在摄食中起重要作用，而且在包括肠道生理学在内的其他功能的中枢调节中也起重要作用。越来越多的证据表明，食欲素在大脑中发挥作用，调节包括胃肠道功能在内的广泛的身体功能。
本综述的目的是总结有关脑食欲素与消化系统的相关发现，并讨论这些肽的病理生理作用，特别参考功能性胃肠疾病。
外源性给予食欲素或内源性释放的食欲素可强烈刺激幽门结扎清醒大鼠的胃酸分泌。迷走胆碱能途径参与了食欲素诱导的胃酸分泌刺激，提示下丘脑外侧区的含食欲素神经元激活延髓背侧运动核中的神经元，从而增加迷走神经传出，刺激胃酸分泌。此外，脑食欲素刺激胃动力、胰腺分泌并诱导胃保护作用。另一方面，脑食欲素参与除了增加食欲之外的许多生理功能，如睡眠/觉醒周期的控制和抗抑郁作用。
从这些证据中，我们提出一个假设，即大脑中食欲素信号的减少可能在部分伴有食欲下降、睡眠障碍、抑郁状态和肠道功能抑制的功能性胃肠疾病患者的病理生理学中起作用。
