Overview of orexin/hypocretin system.

A series of recent studies has established the orexin/hypocretin system as a critical regulator of sleep/wake states. Its deficiency results in the sleep disorder narcolepsy in humans, dogs, and rodents. These findings have brought about the possibility of novel therapies for sleep disorders including narcolepsy and insomnia. Moreover, accumulating evidence indicates that the orexin/hypocretin system regulates sleep and wakefulness through interactions with neuronal systems that regulate emotion, reward, and energy homeostasis. Here, we briefly summarize the progress of orexin/hypocretin studies and future perspectives.