ABSTRACT
There are two known, biologically active hypocretins, hypocretin-1 (orexin A) and hypocretin-2 (orexin B), that are proteolytically derived from preprohypocretin (prepro-orexin) (1,2). In the brain, hypocretins are only produced in a small, scattered group of neurons in the lateral hypothalamus. These neurons have projections throughout the brain, including forebrain, midbrain, hindbrain, and spinal cord (3-5). Notably, hypocretin-containing axons project to nuclei that are integral to the regulation of sleep and wake. Additionally, hypocretin-containing axons innervate areas involved regulating wake-associated functions such as locomotion, sympathetic regulation, and feeding.
