Sakurai T
Institute of Basic Medical Sciences, University of Tsukuba, Ibaraki, Japan.
Regul Pept. 1999 Nov 30;85(1):25-30. doi: 10.1016/s0167-0115(99)00076-2.
Orexin-A and -B are initially identified as endogenous ligands for an orphan G protein coupled receptor. Since the discovery of orexins, investigations of their functions have been guided by their distribution in the lateral hypothalamic area, which has been implicated in feeding behavior. In fact, when administered intracerebroventricularly in early light phase, orexin-A stimulated food consumption. Orexin mRNA is up-regulated by fasting, suggesting their expression is regulated by animal's nutritional status. The orexin neurons project widely in the brain, and thus the physiological role of orexins is likely to be complex. Orexin neurons in the lateral hypothalamic area was shown to receive terminal appositions from NPY-, AgRP-, and a-MSH-IR fibers. The innervation of orexin neurons by peptidergic fibers corresponding to leptin-responsive cell types that reside in the arcuate nucleus may have a role in linking peripheral metabolic cues to autonomic regulatory sites and the cerebral cortical mantle, providing a neuroanatomic basis for regulation of feeding behavior. The wide distribution of orexin-immunoreactive fibers in the brain has also suggested their additional roles. Actually, orexins have been reported to have roles in regulating drinking behavior, neuroendocrine function and the sleep-wake cycle.
食欲素-A和食欲素-B最初被鉴定为一种孤儿G蛋白偶联受体的内源性配体。自从发现食欲素以来，对其功能的研究一直以它们在下丘脑外侧区的分布为导向，而下丘脑外侧区与进食行为有关。事实上，在早光期经脑室注射时，食欲素-A会刺激食物消耗。禁食会使食欲素mRNA上调，这表明它们的表达受动物营养状况的调节。食欲素神经元在大脑中广泛投射，因此食欲素的生理作用可能很复杂。下丘脑外侧区的食欲素神经元被证明接受来自神经肽Y、刺鼠肽基因相关蛋白和α-促黑素免疫反应纤维的终末附着。与位于弓状核的瘦素反应性细胞类型相对应的肽能纤维对食欲素神经元的支配，可能在将外周代谢信号与自主调节位点和大脑皮质联系起来方面发挥作用，为进食行为的调节提供了神经解剖学基础。食欲素免疫反应纤维在大脑中的广泛分布也表明了它们的其他作用。实际上，据报道食欲素在调节饮水行为、神经内分泌功能和睡眠-觉醒周期中发挥作用。
