The role of orexin in motivated behaviours.

Wakefulness and vigilance levels are required for maintaining purposeful activities and motivated behaviours, which are often triggered by sensory information conveying external cues. An increasing body of work has suggested that orexins (also known as hypocretins)--a pair of neuropeptides that are crucial for maintaining wakefulness - are also involved in the regulation of motivated behaviours, including feeding, emotional behaviour and reward seeking, and that these functions are mediated by two subtypes of orexin receptors. Autonomic and endocrine responses, which accompany these motivated behaviours, are also influenced by the orexin system. Orexin-producing neurons act as a hub that links information about the internal and external environments of an animal to vigilance levels and internal bodily functions to support various motivated behaviours.