orexin
Pronunciation: oh-REX-in
A hypothalamic neuropeptide that promotes wakefulness and regulates feeding behavior, deficient in narcolepsy.
Full Definition
Orexin, also known as hypocretin, comprises two neuropeptides (orexin-A and orexin-B) produced exclusively by neurons in the lateral hypothalamus and perifornical area. These peptides act through two G-protein-coupled receptors (OX1R and OX2R) to promote wakefulness, regulate feeding behavior, and maintain sleep-wake stability. Orexin neurons integrate multiple metabolic and circadian signals, including glucose levels, leptin, and light exposure, to coordinate arousal with metabolic demands. The complete loss of orexin-producing neurons causes narcolepsy type 1, characterized by excessive daytime sleepiness, cataplexy, and fragmented nighttime sleep. Cerebrospinal fluid orexin measurements are used diagnostically to distinguish between narcolepsy subtypes.
Usage
Usage note: Hypocretin and orexin refer to the same peptides; ensure terminology consistency within documents based on preferred journal style.
In Context
- "Cerebrospinal fluid orexin levels were undetectable, confirming the diagnosis of narcolepsy type 1." — Sleep medicine consultation note
- "Orexin receptor antagonists showed promise as novel treatments for insomnia in clinical trials." — Pharmaceutical research report