Neuropeptides that play a significant role in the regulation of food intake and sleep-wakefulness, possibly by coordinating the complex behavioral and physiologic responses of these complementary homeostatic functions. A broader role in the homeostatic regulation of energy metabolism, autonomic function, hormonal balance and the regulation of body fluids, is also suggested. Orexin-A binds to both OX1R and OX2R with a high affinity, whereas orexin-B binds only to OX2R with a similar high affinity. Associated with perikaryal rough endoplasmic reticulum as well as cytoplasmic large granular vesicles at synapses. Restricted to neuronal cell bodies of the dorsal and lateral hypothalamus. Specific enzymatic cleavages at paired basic residues yield the different active peptides. Belongs to the orexin family. Qui dort dine - Issue 15 of October 2001