orexin
noun
orex·in
| \ ə-ˈrek-sən
\
\
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