Orexins are involved with normal and compulsive motivated behaviors. Orexin, also known as hypocretin, is a neuropeptide that regulates arousalwakefulness, and appetite. There is a high affinity between the orexin system in the rat brain and that in the human brain. High levels of orexin-A have been associated with happiness in human subjects, while low levels have been associated with sadness. Findings suggest that boosting levels of orexin-A could elevate mood in humans, being thus a possible future treatment for disorders like depression.