Orexin

Orexin, also called hypocretin, is a pair of neuropeptides made mainly by neurons in the hypothalamus. They help stabilize wakefulness and also influence appetite, reward, and autonomic functions.

Orexin A: A 33-amino-acid neuropeptide that activates both orexin receptors. It is one of the two peptides released by orexin-producing neurons.
Narcolepsy: A chronic neurological disorder involving unstable sleep–wake states and, in type 1, loss of orexin-producing neurons. Loss of orexin signaling is a defining cause of narcolepsy type 1.
Masashi Yanagisawa: A Japanese physiologist whose research identified orexin peptides and receptors. His team discovered the peptides while searching for ligands of orphan receptors.
Cataplexy: A sudden, brief loss of muscle tone, often triggered by strong emotion and occurring in narcolepsy type 1. Orexin deficiency can destabilize control of muscle tone during wakefulness.
Orexin B: A 28-amino-acid neuropeptide that activates both orexin receptors, with greater selectivity for OX2R. It is the second peptide made from the orexin precursor.
Suvorexant: A dual orexin receptor antagonist used to treat insomnia. It promotes sleep by blocking both orexin receptors.
Louis de Lecea: A neuroscientist who independently identified hypocretin peptides and their hypothalamic expression. His group named the system hypocretin and connected it to hypothalamic signaling.
Sleep paralysis: A temporary inability to move or speak while falling asleep or waking, despite awareness. Unstable boundaries between sleep and wakefulness in narcolepsy can produce this symptom.
Orexin receptor 1: A G-protein-coupled receptor for orexin peptides, also called OX1R. Its signaling helps connect orexin to arousal and reward-related pathways.
Lemborexant: A dual orexin receptor antagonist prescribed for insomnia in adults. It suppresses orexin-driven wakefulness through both receptor subtypes.

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