Quick summary
Nociceptin is a 17-amino acid neuropeptide activating the NOP receptor, which does not couple to reward pathways -- making it a target for non-addictive analgesics. Cebranopadol shows efficacy in Phase II/III pain trials.
Overview
Nociceptin (Orphanin FQ) is a 17-amino acid neuropeptide and the endogenous ligand for the NOP receptor (ORL-1, opioid receptor-like 1). Structurally related to the opioid peptide dynorphin, nociceptin activates an opioid-like receptor but does not bind classical mu, kappa, or delta opioid receptors. It produces complex, site-dependent effects on pain modulation and is studied as a non-addictive analgesic target due to the absence of classical opioid reward signaling.
Mechanism of action
Nociceptin binds selectively and with high affinity to the NOP receptor, activating Gi/Go proteins to inhibit adenylyl cyclase, decrease cAMP, suppress voltage-gated calcium channels, and activate inwardly rectifying potassium channels. These actions reduce neuronal excitability. Supraspinally, NOP activation counteracts opioid analgesia and morphine-induced reward, while spinally and peripherally it produces analgesic effects. The absence of NOP receptor coupling to the mesolimbic dopamine reward pathway distinguishes nociceptin from classical opioids, supporting its non-addictive profile.
Dosing protocols
| Purpose | Route | Dosage | Frequency | Notes |
|---|---|---|---|---|
| pain / NOP receptor research (animal) | intravenous | 1–30 nmol/kg | per experimental protocol (often intrathecal or ICV in animal studies) |
Dosing information is for educational purposes only. Consult a qualified healthcare professional before using any peptide.
Research summary
NOP receptor research has identified nociceptin as a modulator of pain, anxiety, stress, reward, and memory. Selective NOP receptor ligands are in clinical development: cebranopadol (mixed NOP/opioid agonist) has shown efficacy in phase II/III trials for chronic low back pain. Sunobinop (partial NOP agonist) promotes non-REM sleep in rodents and early human trials. The NOP system's ability to reduce opioid tolerance and reward makes it a target for opioid use disorder research. Nociceptin also modulates immune function and cardiovascular tone.[1][2][3][4]
Evidence grading
Each claimed benefit is graded by the strength of available evidence. Grades reflect study quality, not effect size.
Strong = multiple RCTs · Moderate = limited trials or observational · Preliminary = animal or in vitro only · Insufficient = anecdotal or no published data
Side effects
Side effects vary by individual. This is not an exhaustive list. Report unusual symptoms to a healthcare professional.
Common stacks
Peptides commonly paired with Nociceptin for synergistic effects.
Legal status
Nociceptin peptide is available for laboratory research only. NOP receptor-targeting drugs in clinical trials (cebranopadol, sunobinop) are investigational agents, not approved for general use.
Sourcing & access
Research compound
Nociceptin is classified as a research compound. Regulatory status varies by jurisdiction. Always verify current legal status and source from vendors providing third-party certificates of analysis (COA).
Frequently asked questions
Nociceptin, also called Orphanin FQ, is a 17-amino acid neuropeptide and the endogenous ligand for the NOP receptor (ORL-1). It is structurally related to dynorphin but does not bind classical mu, kappa, or delta opioid receptors, producing complex site-dependent effects on pain modulation.
Nociceptin binds the NOP receptor, activating Gi/Go proteins to inhibit adenylyl cyclase, suppress calcium channels, and activate potassium channels. Supraspinally, NOP activation counteracts opioid analgesia and reward, while spinally it produces analgesic effects. The absence of mesolimbic dopamine reward coupling distinguishes it from classical opioids.
Nociceptin is a research compound with effects including reduced locomotion at high doses, anxiolytic effects, and potential anti-analgesic effects at supraspinal sites. It is rapidly degraded by peptidases with a half-life of 3-5 minutes. No approved therapeutic applications exist for the peptide itself.
The NOP system's ability to reduce opioid tolerance and reward without activating the dopamine reward pathway makes it a target for non-addictive analgesics. Cebranopadol (mixed NOP/opioid agonist) has shown efficacy in Phase II/III trials for chronic low back pain, and sunobinop promotes non-REM sleep.
Research references
- Nociceptin/orphanin FQ: a novel neuropeptide with anti-opioid and pain-modulating propertiesPubMed
- NOP receptor agonists and nociceptin in pain, anxiety, and drug addictionPubMed
- Nociceptin and stress: central effects on the hypothalamic-pituitary axisPubMed
- Nociceptin/orphanin FQ as a target for novel analgesic drug developmentPubMed