Neuropeptide AF (NPAF)
The 18-amino-acid sister of neuropeptide FF — an RFamide peptide that curbs appetite, modulates pain and opioid analgesia, and activates the stress axis. A research peptide, not a drug
Neuropeptide AF (NPAF) is an 18-amino-acid signalling peptide of the RFamide family — so called because, like its relatives, it ends in the amino-acid signature arginine-phenylalanine-amide (…Arg-Phe-NH2). It is cut from the same precursor protein as the better-known neuropeptide FF (NPFF), and the two share the brain's NPFF receptors, NPFF-R1 and NPFF-R2. NPAF is best known as part of the body's pain-modulating, 'anti-opiate' system: it tunes how strongly opioids relieve pain. But research has widened its picture considerably. Given into the brain of rodents and birds it reduces food intake, acting through the hypothalamus and the appetite-controlling melanocortin system, which makes it a point of interest for appetite biology. It also switches on the hypothalamic-pituitary-adrenal stress axis, raising stress hormones, and in behavioural tests it produces anxiety-like and, paradoxically, antidepressant-like effects, and can improve memory in a learning task. NPAF is an endogenous neuropeptide studied as a research tool; it is not an approved medicine and has not been given to people as a treatment.
No established human dose Details ↓
Recommended Dosing
No established human dose
Neuropeptide AF is an endogenous peptide that has never been given to people as a treatment. The work is in animals and cells, where NPAF is injected into the brain at experimental amounts that do not carry over to people.
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What is it?
The RFamide peptides are a family of brain signalling molecules that all end in the arginine-phenylalanine-amide motif. Neuropeptide AF (NPAF) belongs to this family and is cut from the same precursor protein as neuropeptide FF (NPFF); the two are sister peptides that act on the shared NPFF receptors NPFF-R1 and NPFF-R2. NPAF is an amidated 18-amino-acid peptide, and structural work by NMR has mapped it as a largely helical peptide whose C-terminal tail is what the receptor recognises.
NPAF's original claim to fame is pain. Like NPFF, it is an 'anti-opiate' peptide — it modulates how strongly opioids relieve pain and participates in the body's own pain-control circuits. Work on cells of the gut has also shown NPAF can trigger a gentle, piecemeal release of mediators from mucosal mast cells, hinting at a role in the cross-talk between nerves and the immune system in the intestine.
A large strand of research concerns appetite. Delivered into the brain, NPAF reduces food (and water) intake in chicks, quail and rats. In quail this anorexia is tied to activation of the hypothalamus and the appetite-suppressing melanocortin system (more pro-opiomelanocortin and melanocortin-4-receptor signalling, less corticotropin-releasing factor), and in selectively bred chickens the sensitivity to NPAF differs between lean and heavy lines. In rats the effect is a short-term, dose-dependent dip in feeding.
NPAF also acts on mood and the stress system. Injected into the brain of rats it raises the stress hormones ACTH and corticosterone through corticotropin-releasing hormone, increases exploratory movement and grooming, and reduces time spent in the open arms of a maze — an anxiety-like signature. In mice it likewise produces anxiety-like behaviour but, in a forced-swim test, an antidepressant-like effect that depends mainly on serotonin signalling; and in a passive-avoidance task NPAF improved memory consolidation and even reversed a beta-amyloid-induced memory deficit.
NPAF is an endogenous research peptide, not a medicine. No published study has given NPAF to people as a treatment — the work is in animals and cells — it is approved nowhere, and material sold online as 'neuropeptide AF' is an unregulated research chemical. Nothing here is a dose or a therapy; this page records what the published science says about the peptide.
Mechanism of Action
Neuropeptide AF is an RFamide octadecapeptide cut from the NPFF precursor, the sister peptide of neuropeptide FF, and signals through the NPFF receptors NPFF-R1 and NPFF-R2. Through these it modulates pain and opioid analgesia, reduces food intake via the hypothalamic melanocortin system, and activates the HPA stress axis with associated effects on mood and memory.
NPFF-receptor signalling
NPAF binds the G-protein-coupled NPFF receptors NPFF-R1 and NPFF-R2 (shared with NPFF); its C-terminal RFamide tail drives receptor recognition (PMID 12767123).
Appetite suppression (melanocortin system)
Given centrally, NPAF reduces food intake in rodents and birds (PMID 21147172), activating hypothalamic satiety nuclei and the pro-opiomelanocortin / melanocortin-4-receptor pathway while lowering CRF (PMID 34023535).
Stress axis, mood and pain modulation
NPAF activates the HPA axis via corticotropin-releasing hormone and dopamine, producing anxiety-like behaviour (PMID 19269292) and a serotonin-dependent antidepressant-like effect (PMID 25116251), as part of the RFamide anti-opiate pain-modulating system.
Published Research
These are studies of neuropeptide AF read from their PubMed abstracts on November 6, 2026. They include the determination of the human NPAF sequence and structure, a cell study of its action on mucosal mast cells, and animal studies of its effects on the stress axis and behaviour, on anxiety- and antidepressant-like behaviour, and on food intake (including its link to the melanocortin system). NPAF has not been given to people as a treatment in any published study; the evidence is animal and cell work.
The structure of neuropeptide AF
NMR structure determination of human NPAF (sequence AGEGLNSQFWSLAAPQRF-NH2), a pain-modulating and anti-opiate peptide acting at an orphan G-protein-coupled receptor. In both a membrane-mimetic micelle and a trifluoroethanol/water system the peptide was mainly alpha-helical through its centre (Asn6-Ala14) with a random N-terminus; the C-terminal tetrapeptide formed a turn and was shown to be important for receptor recognition (a structural study).
NPAF acts on intestinal mucosal mast cells
In murine bone-marrow-derived mucosal mast cells, NPAF induced a slow 'piecemeal' degranulation (measured by a beta-hexosaminidase assay, mast-cell protease ELISA, electron microscopy and calcium imaging). The mast cells and enteric neurons expressed the NPFF precursor and candidate receptors, but knocking out two Mas-related receptors did not block the effect, so the response was receptor-independent — positioning NPAF as a possible mediator in nerve-immune communication in the gut (a cell study).
Endocrine, behavioural and autonomic effects of NPAF in rats
Given into the brain of rats, NPAF stimulated release of the stress hormones ACTH and corticosterone — an effect blocked by a corticotropin-releasing-hormone (CRH) receptor antagonist — activated exploratory locomotion and grooming, reduced entries to the open arms of an elevated-plus maze (anxiety-like), tended to lower body temperature and heart rate, and increased dopamine release from brain slices. NPAF acts on the HPA stress axis and behaviour through CRH and dopamine (a preclinical result).
NPAF induces anxiety-like and antidepressant-like behaviour in mice
In mice, NPAF decreased immobility and increased climbing and swimming in a forced-swim test — an antidepressant-like effect reversed mainly by the serotonin antagonist methysergide and partly by atropine — while in an elevated-plus maze it reduced open-arm time (anxiety-like). The antidepressant-like action is mediated chiefly through 5-HT2 serotonergic and muscarinic cholinergic signalling, and the anxiety-like effect, seen earlier in rats, proved species-independent (a preclinical result).
NPAF suppresses appetite via the melanocortin system
In Japanese quail, NPAF given into the brain reduced food and water intake dose-dependently, raised c-Fos activity in the paraventricular, ventromedial and dorsomedial hypothalamic nuclei, lowered corticotropin-releasing-factor messenger RNA and increased pro-opiomelanocortin and melanocortin-4-receptor messenger RNA. The anorexigenic effect of NPAF is associated with activation of the hypothalamic melanocortin system (a preclinical result).
NPAF reduces short-term food intake in rats
Neuropeptide AF given into the brain of rats produced a linear, dose-dependent reduction in cumulative food intake over three hours (significant at the half-hour mark on a non-cumulative basis) — reported as the first demonstration of NPAF-induced reduction of food intake in a mammalian model (a preclinical result).
No Established Human Dose
Neuropeptide AF is an endogenous peptide that has never been given to people as a treatment. The work is in animals and cells, where NPAF is injected into the brain at experimental amounts that do not carry over to people. No regulator has approved any dose, and no published human dose exists, so no amount is printed here.
What this rests on: PMID 19269292, PMID 34023535, PMID 21147172.
Educational information, not medical advice. The doses on this page come from approved labels, published studies and, where no study exists, amounts reported by users. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose. Full medical disclaimer.
What a Buyer Needs to Know
What is sold, how it is mixed, stored and taken, and what is known about its safety, quality and legal status. Each part names its source. Where we have none, it says unknown.
What is sold
Unknown: we hold no label and no published test that says what forms or vial sizes Neuropeptide AF (NPAF) is sold in. A vial's own label is a seller's claim, not a source.
Mixing a vial: a worked example
Unknown: no human dose of Neuropeptide AF (NPAF) has been established (see No Established Human Dose below), so there is no amount to work out. The reconstitution calculator does the arithmetic for any vial, water and dose.
Storage before and after mixing
Unknown: no label or published stability study on file says how to store Neuropeptide AF (NPAF), before or after mixing. The mixing guide sets out the general rules, with their sources: keep a mixed vial in the fridge, and use it promptly, as the bacteriostatic water label says of any drug dissolved in it. The 28 days often quoted is the limit for an opened multiple-dose vial from a manufacturer, an outer limit set for sterility, not a time a mixed solution has been shown to keep. Nobody has published how long Neuropeptide AF (NPAF) stays intact once mixed.
How it is taken
Unknown: with no established human dose, there is no established way of taking Neuropeptide AF (NPAF). What the human studies gave and how is set out under No Established Human Dose.
What to expect, and when
How long it stays in the body: a half-life of not established for humans as a drug; an endogenous neuropeptide. After about five half-lives almost none is left.
When effects appear: unknown; no source on this page gives a time to effect for Neuropeptide AF (NPAF). Results reported in the studies are under Published Research.
Source: half-life: PMID 12767123.
Side effects, and when to stop or get help
From the Side Effects section: No human adverse-event data exist: no published study has administered NPAF to people; In animals, centrally given NPAF raises stress hormones and produces anxiety-like behaviour (PMID 19269292) and reduces food intake (PMIDs 34023535, 21147172) — preclinical signals, not a human safety profile; It modulates pain and opioid analgesia as part of the 'anti-opiate' RFamide system, which is why its interactions with opioids are studied in animals; Material sold online as 'neuropeptide AF' is an unregulated research chemical of unverified content. Full list and cautions ↓
When to stop or get help: unknown; no label or trial on file sets rules for stopping Neuropeptide AF (NPAF). Treat a severe or unexpected reaction as a reason to stop and see a doctor.
Source: the Side Effects section below (“Neuropeptide AF is a research peptide that has not been given to people as a drug, so there is no human safety profile; the points below reflect that research status”).
Interactions
Unknown: a PubMed search for human interaction studies of Neuropeptide AF (NPAF) (reviewed 2026-11-06) found none. Unknown is not the same as safe to combine.
Every peptide's record, with its source: the interaction matrix.
Checking what you bought
Unknown: no published independent test of Neuropeptide AF (NPAF) products is in our lab-results database yet, so how products sold under this name measure up is not known.
To read a certificate of analysis, paste it into the COA decoder. Trust & Verification explains what independent testing can and cannot show.
Legal status
US: Research Chemical (Not a drug: Drugs@FDA and the openFDA label endpoint hold no record, and FDA GSRS and ChEMBL hold no substance record for neuropeptide AF (searched November 6, 2026)). Sport: Not on the 2026 List.
Country by country ↓ · Regulatory tracker
Source: this entry's approval status and the WADA Prohibited List, as in Legal Status below.
Side Effects & Contraindications
Reported Side Effects
Neuropeptide AF is a research peptide that has not been given to people as a drug, so there is no human safety profile; the points below reflect that research status.
Contraindications & Cautions
Neuropeptide AF has no approved use and no label. These points reflect its research status.
Legal Status
Neuropeptide AF is an endogenous peptide studied as a research compound; it is not a drug and is not approved in any country.
Frequently Asked Questions
?What is neuropeptide AF?
An 18-amino-acid RFamide neuropeptide (human sequence AGEGLNSQFWSLAAPQRF-NH2) cut from the same precursor as neuropeptide FF. The two are sister peptides that act on the shared NPFF receptors NPFF-R1 and NPFF-R2.
?What does it do?
It is part of the body's pain-modulating, 'anti-opiate' system, and research shows it also reduces food intake through the hypothalamic melanocortin system (PMIDs 34023535, 21147172) and activates the stress axis, with anxiety-like and antidepressant-like effects in animals (PMIDs 19269292, 25116251).
?How is it related to neuropeptide FF?
Both NPAF and NPFF are cleaved from the same NPFF precursor gene and act on the same NPFF receptors. They are studied together as RFamide anti-opiate peptides; Grey Peptides has a separate entry for neuropeptide FF.
?Is it approved or available to buy?
No. Neuropeptide AF is not a medicine, has no FDA application or label, and is approved nowhere. Material sold online as neuropeptide AF is an unregulated research chemical. Grey Peptides lists no sellers and recommends no source; this page records the published science.
References
- [mechanism] Miskolzie M, et al. "The NMR-derived conformation of neuropeptide AF, an orphan G-protein coupled receptor peptide." Biopolymers, 2003;69(2):201-15. PMID: 12767123.
- [mechanism] Abdellah N, et al. "Neuropeptide AF Induces Piecemeal Degranulation in Murine Mucosal Mast Cells: A New Mediator in Neuro-Immune Communication in the Intestinal Lamina Propria?." Anat Rec (Hoboken), 2018;301(6):1103-1114. PMID: 29346716.
- [animal] Jászberényi M, et al. "Endocrine, behavioral and autonomic effects of neuropeptide AF." Horm Behav, 2009;56(1):24-34. PMID: 19269292.
- [animal] Palotai M, et al. "Neuropeptide AF induces anxiety-like and antidepressant-like behavior in mice." Behav Brain Res, 2014;274:264-9. PMID: 25116251.
- [animal] Bohler M, et al. "The anorexigenic effect of neuropeptide AF in Japanese quail, Coturnix japonica, is associated with activation of the melanocortin system." Comp Biochem Physiol A Mol Integr Physiol, 2021;259:110982. PMID: 34023535.
- [animal] Newmyer BA, et al. "Neuropeptide AF is associated with short-term reduced food intake in rats." Behav Brain Res, 2011;219(2):351-3. PMID: 21147172.
- [other] UniProt O15130 (pro-FMRFamide-related neuropeptide FF precursor, NPFF gene), read November 6, 2026: neuropeptide AF (NPAF) is one of the bioactive peptides cleaved from this precursor (which also yields neuropeptide FF); the human peptide is the amidated octadecapeptide Ala-Gly-Glu-Gly-Leu-Asn-Ser-Gln-Phe-Trp-Ser-Leu-Ala-Ala-Pro-Gln-Arg-Phe-NH2 (AGEGLNSQFWSLAAPQRF). https://www.uniprot.org/uniprotkb/O15130/entry
- [other] The human NPAF sequence (AGEGLNSQFWSLAAPQRF-NH2) and its structure as an orphan G-protein-coupled-receptor peptide of the RFamide family were reported in the NMR conformation study carded on this page; NPAF signals through the NPFF receptors NPFF-R1 and NPFF-R2 (read November 6, 2026).
- [other] US FDA, Drugs@FDA and the drug label endpoint (openFDA), searched November 6, 2026: no application and no label record for neuropeptide AF. It is an endogenous neuropeptide, not a registered drug; FDA GSRS and ChEMBL hold no substance record for it.
Sources & Citations
The six studies carded above were read from their PubMed records on November 6, 2026. Identity comes from UniProt (O15130, the pro-FMRFamide-related NPFF precursor that also yields neuropeptide FF) and the NMR structure study carded here, which reports the human sequence AGEGLNSQFWSLAAPQRF-NH2; NPAF's signalling through the NPFF receptors, its anti-opiate pain modulation, its reduction of food intake via the melanocortin system, and its effects on the stress axis and behaviour are from the studies carded on this page; the absence of US approval and of a drug substance record from Drugs@FDA, openFDA, FDA GSRS and ChEMBL was checked the same day. Grey Peptides sells nothing and links to no vendor.
Medical Disclaimer: This content is for educational and informational purposes only. It is not medical advice, and nothing here is an instruction to obtain or use any compound. Talk to a licensed clinician about your own situation.