orexin

noun
orex·​in | \ ə-ˈrek-sən How to pronounce orexin (audio) \

Medical Definition of orexin

: either of two neuropeptides ( orexin A and orexin B ) that are produced in the hypothalamus and play a role in regulating wakefulness and food intake Scientists have known for almost a decade that narcolepsy is caused by a dearth of a brain communication chemical called orexin.— Laura Sanders, Science News, 24 Oct. 2009 The new sleep aids block the activity of brain peptides called orexins.— Christine Soares, Scientific American, July 2010

called also hypocretin

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a strong desire or propensity

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