Orexin is a neurotransmitter that mainly regulates sleep/wake cycle. In addition to its sleep cycle regulatory role, it is involved in regulation of attention, energy homeostasis, neurogenesis and cognition. Several evidences has shown the involvement of orexin in narcolepsy, but there are also growing evidences that shows the disturbance in orexin system in neurodegenerative diseases including Alzheimer's, Parkinson's, Epilepsy, Huntington's diseases and Amyotrophic lateral sclerosis. Pathogenesis and clinical symptoms of these disorders can be partly attributed from orexin system imbalance. However, there are controversial reports on the exact relationship between orexin and these neurodegenerative diseases. Therefore, the aim of this review is to summarize the current evidences regarding the role of orexin in these neurodegenerative diseases.

食欲素是主要调节睡眠/唤醒周期的神经递质。除了其睡眠周期调节作用外，它还参与注意力，能量稳态，神经发生和认知的调节。已有几项证据表明食欲素与发作性睡病有关，但越来越多的证据表明食欲素系统在神经退行性疾病（包括阿尔茨海默氏病，帕金森氏病，癫痫症，亨廷顿氏病和肌萎缩性侧索硬化症）中受到干扰。这些疾病的发病机理和临床症状可部分归因于食欲素系统失衡。但是，有关于奥瑞辛与这些神经退行性疾病之间确切关系的报道。因此，