[Orexins--new hypothalamic peptides that stimulate appetite].

A family of novel hypothalamus-specific peptides called orexins have recently been discovered and characterized. The orexins stimulate appetite (the greek word orexis means appetite) when given intraventricularly to rats. Their genes are expressed bilaterally in the lateral hypothalamus, a region previously known to regulate food intake. The two peptides, orexin A (33 amino-acids) and orexin B (28 amino acids), are derived from a common prepro-orexin precursor. The peptides bind to specific G-protein-coupled orexin receptors termed OX-1R and OX-2R. The identification of the orexins will increase our understanding on how the brain regulates food intake.