Orexin-B (Hypocretin-2)
Orexin-B (hypocretin-2) is a 28-aa hypothalamic neuropeptide that activates OX2R > OX1R to promote wakefulness and regulate sleep/appetite. Loss of orexin neurons causes narcolepsy. Orexin receptor antagonists are approved for insomnia.
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Compound Profile
Orexin-B (Hypocretin-2)
Key Data
Research reference only
Research Focus
Preclinical data
⚠ Research & Educational Use Only. Orexin-B (Hypocretin-2) is a research chemical documented here for scientific education. All information references peer-reviewed literature and preclinical/clinical study data. Not for human consumption. Not medical advice. Consult a licensed researcher or healthcare professional before any laboratory use.
- Potent wakefulness promotion via OX2R (and OX1R) in the locus coeruleus, dorsal raphe, and histaminergic neurons
- Suppresses REM sleep and maintains stable wakefulness state transitions
- Regulates appetite and energy balance via hypothalamic OX receptors
- Orexin-B (Hypocretin-2) is not FDA-approved for human use. It is a research chemical for scientific study only.
Research At a Glance
- Potent wakefulness promotion via OX2R (and OX1R) in the locus coeruleus, dorsal raphe, and histaminergic neurons
- Suppresses REM sleep and maintains stable wakefulness state transitions
- Regulates appetite and energy balance via hypothalamic OX receptors
- Activates reward pathways (mesolimbic dopamine) — relevant to addiction and motivation research
In Plain English
Simple summaryOrexin-B (hypocretin-2) is a 28-amino acid neuropeptide produced by the same small cluster of lateral hypothalamus neurons that produce orexin-A. The two orexins are synthesized from the same precursor protein (prepro-orexin) and work together to maintain wakefulness and regulate arousal, but they have different receptor selectivity: orexin-A activates both OX1 and OX2 receptors with high affinity, while orexin-B has much lower affinity for OX1 and mainly works through OX2. OX2 is particularly important for the wakefulness-promoting effects of the orexin system -- the insomnia drugs suvorexant, lemborexant, and daridorexant block OX2 (among other targets) to achieve their sleep-promoting effect. Narcolepsy results from loss of both orexins, and the CSF diagnostic test measures orexin-A specifically.
- Potent wakefulness promotion via OX2R (and OX1R) in the locus coeruleus, dorsal raphe, and histaminergic neurons
- Suppresses REM sleep and maintains stable wakefulness state transitions
- Regulates appetite and energy balance via hypothalamic OX receptors
The full scientific detail, mechanisms, citations, and dosing data, follows below.
What is Orexin-B (Hypocretin-2)?
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Orexin-B (also called hypocretin-2) is a 28-amino acid neuropeptide produced exclusively by neurons in the lateral hypothalamic area (LHA). It is one of two orexin peptides — the other being Orexin-A (33 amino acids, also documented in this database). Both peptides are derived from the same 130-amino acid precursor protein, prepro-orexin.
Orexin-B was discovered simultaneously by two groups in 1998: Sakurai et al. (Cell, named orexin from the Greek "orexis" = appetite) and de Lecea et al. (PNAS, named hypocretin from hypothalamus + secretin-like structure). The peptides activate two G-protein-coupled receptors: OX1R and OX2R.
**Receptor selectivity:** - **OX1R (orexin receptor 1)**: Prefers Orexin-A; Gq-coupled; mediates some reward and stress circuits - **OX2R (orexin receptor 2)**: Binds both Orexin-A and Orexin-B with similar affinity; Gq- and Gi-coupled; critical for wakefulness maintenance
Orexin-B's pharmacological distinction from Orexin-A is its relatively higher OX2R selectivity, which is the primary receptor mediating wakefulness (based on pharmacological and genetic studies).
**Narcolepsy and orexin deficiency:** The critical importance of orexin research came from the discovery that narcolepsy type 1 is caused by loss of orexin neurons (due to autoimmune destruction in most patients). This results in: cataplexy (sudden loss of muscle tone triggered by emotion), excessive daytime sleepiness, sleep paralysis, and hypnagogic hallucinations. Orexin/hypocretin deficiency in CSF is a diagnostic criterion for narcolepsy type 1.
**Therapeutic implications:** - Insomnia treatment: Dual orexin receptor antagonists (DORAs) — suvorexant (Belsomra), lemborexant (Dayvigo), daridorexant (Quviviq) — block orexin signaling to allow sleep onset and maintenance - Narcolepsy treatment: OX2R agonists (TAK-994, Takeda) are in Phase II trials to replace lost orexin signaling in narcolepsy type 1 - Other research: Addiction (orexin modulates drug reward and reinstatement), anxiety (OX1R in fear circuits), and metabolic research (orexins regulate energy expenditure)
By the Numbers
Key Research Benefits
Documented effects observed in preclinical and clinical studies on Orexin-B (Hypocretin-2). See all Cognitive Enhancement peptides for comparison.
Side Effects & Risks
Adverse effects reported in the research literature. All data sourced from preclinical and clinical study reports. View all peptides' side effects →
Dosing Data from the Literature
Doses referenced below are sourced from published preclinical and clinical studies. Use the peptide dose calculator to convert these values to injection volume.
Orexin-B research protocols (CNS research tools):
ICV injection (rodent sleep studies): 3-30 nmol for wake-promoting effects IV injection: 1-10 nmol/kg for peripheral cardiovascular/autonomic studies OX2R agonism: Used to model hypersomnia/narcolepsy reversal in orexin-deficient animal models
Drug development focus is on OX receptor antagonists (suvorexant/Belsomra 5-20 mg, lemborexant/Dayvigo 5-10 mg) and OX2R agonists (TAK-994, currently in Phase II for narcolepsy type 1)
Administration in Research Settings
Standard reconstitution and administration methodology for laboratory research use.
Orexin-B is used as a research peptide for CNS studies requiring ICV or direct brain injection protocols. Poor blood-brain barrier penetration of the native peptide limits IV utility for central effects. Small molecule OX2R agonists have better CNS bioavailability.
What the research doesn't show
In clinical practice, the orexin-A/orexin-B distinction matters mainly for research pharmacology. Both orexins are lost in narcolepsy. The sleep drugs that target the orexin system block both receptors because the cleaner sleep profile comes from dual blockade. For anyone studying the basic science of arousal circuits, the OX1 vs OX2 distinction is important; for most clinical applications, the pair is treated as a unit.
Medical Expert Videos
Physicians, researchers, and pharmacologists explain Orexin-B (Hypocretin-2), covering mechanisms of action, clinical context, and study findings.
Videos sourced from YouTube search. KnowYourPeptide does not endorse any individual creator. For research education only.
The Bottom Line
Orexin-B (Hypocretin-2) has a growing body of preclinical evidence and a well-characterised safety profile in research settings. The most-studied application is: potent wakefulness promotion via ox2r (and ox1r) in the locus coeruleus, dorsal raphe, and histaminergic neurons.
The most commonly reported side effect in research subjects is cns-penetrating ox agonism could worsen symptoms in individuals with hyperactive orexin states (anxiety, insomnia). It is a research chemical, not approved for human use.
Frequently Asked Questions
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How It Compares
Orexin-A activates both OX1 and OX2, making it more pharmacologically complex. OX1 appears more involved in emotional memory and stress responses; OX2 in wakefulness and circadian regulation. The approved sleep drugs (suvorexant, lemborexant, daridorexant) are 'dual orexin receptor antagonists' (DORAs) blocking both -- selective OX2 antagonists (SORAs) have also been developed and achieve similar sleep effects with potentially fewer emotional side effects.
Compare Orexin-B (Hypocretin-2) side-by-sideResearch Use Only
This information is for educational research purposes only. This is not medical advice. Consult a qualified healthcare professional.