Definition of orexin in US English:



  • Either of two hormones (orexin-A or orexin-B) produced by the mammalian hypothalamus and functional in the regulation of appetite and sleep.

    Also called hypocretin
    • ‘Human narcolepsy generally stems from a shortage of the neurons, which produce the excitatory neurotransmitter known both as hypocretin and orexin.’
    • ‘The lateral hypothalamus contains cells that secrete a protein neurotransmitter called ‘orexin’ or ‘hypocretin.’’
    • ‘For example, physical activity increased in rats when injected with orexin, a brain chemical associated with sexual arousal.’
    • ‘Orexin A is a promising candidate to become a "sleep replacement" drug.’
    • ‘Orexin neurons are exclusively localized in the lateral hypothalamic area and project their fibers to the entire central nervous system.’