The hypothalamus acts as a major regulatory center involved in the control of feeding behavior and energy homeostasis. Several neuropeptides and proteins have been shown to be involved in the regulation of these processes. Orexin A (hypocretin 1) a 33 amino acid peptide and orexin B(hypocretin 2), a 28 amino acid peptide, are both derived from a common 130 amino acid precursor, prepro-orexin, which is encoded by a gene localized to human chromosome 17q21. Orexin A and Orexin B stimulate food consumption when administered intracerebroventricularly to rats. Orexin gene expression in the brain is highly restricted to distinct populations of neurons located in specific hypothalamic regions, including the lateral hypothalamic area (LHA), a region implicated in feeding behavior.