Naheed Anwar, Taimur Saleem, Umair Khalid, Sheikh Abdul Saeed.
Discovery of orexins/hypocretins: their roles in regulating the hypothalamic pituitary gonadal axis.
Pak Armed Forces Med J Jan ;58(4):446-54.

Orexin A and B, also named hypocretin 1 and 2, were identified in 1998 by two independent research groups led by Sutcliffe and Yanagisawa, respectively. Both peptides are derived from a common precursor containing 130 amino acids (aa), called prepro-orexin. Orexin A is a 33-aa peptide, while orexin B is a 28-aa peptide. Both peptides act on their targets via two G- protein coupled receptors (OX1 and OX2) which mobilize Ca++. Orexin A is highly conserved among human, pig, dog, rat and mouse whereas orexin B differs by 2 aa residues in rats and mouse from human. Diverse responses of orexin containing hypothalamic neurons include feeding behavior, sleep-wakefulness, neuroendocrine and, autonomic regulation and reproduction. Although, identified in the hypothalamus, expression of orexins and their receptors have been found in a variety of peripheral tissues. In the present review, we especially focus on the nomenclature and discovery of orexins, their localization in CNS and peripheral sites, genetics and structural constitution of orexins, their receptors, physiological actions, and roles in the regulation of hypothalamic- pituitary- gonadal axis.

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