NPFF: brain peptide that modulates pain and opioid effects
A naturally occurring signaling molecule in the brain that shapes how the body processes pain, regulates opioid effects, and influences heart function; used only as a lab research tool.
A researcher, an agent, or an algorithm wrote down the sequence and picked a target to hit.
An AI model like OpenFold3 or AlphaFold built a 3D structure and scored how well it fits the binding site.
A second contributor repeated the computation on their own hardware and the scores matched.
A chemistry service or a researcher ordered the sequence, it was manufactured, and mass spectrometry confirmed the right molecule was produced.
A binding or activity measurement confirmed that it actually does what the computer predicted — or didn't.
What this is
Neuropeptide FF (NPFF) is a short, naturally occurring brain peptide — eight amino acids long (FLFQPQRF) — that acts as a signaling molecule in the central nervous system. Its name comes from the two phenylalanine residues that bookend the sequence (F...F), a hallmark of the broader "RFamide" peptide family to which it belongs. The mature peptide carries a C-terminal amide cap (FLFQPQRF-NH₂) that is essential for receptor binding but is not represented in the raw 8-letter sequence stored on this card. NPFF is best known to neuropharmacologists as a modulator of opioid analgesia, pain processing, food intake, and cardiovascular tone.
History
NPFF was first identified in mammalian brain in the mid-1980s during a search for endogenous peptides resembling the molluscan neuropeptide FMRFamide. An early study (Yang and colleagues, PNAS 1985) reported that the octapeptide FLFQPQRF-NH₂ could attenuate morphine's behavioral effects in rats, establishing NPFF as an "anti-opioid" peptide and triggering decades of follow-up work on its role in opioid tolerance. Phylogenetic analysis later placed NPFF within a family of five vertebrate RFamide groups — NPFF, prolactin-releasing peptide (PrRP), kisspeptin, neuropeptide VF/RFRP, and 26RFa/QRFP — all sharing the C-terminal Arg-Phe-NH₂ motif (J Neuroendocrinol 2010).
What it does
NPFF acts on neurons by binding two G-protein-coupled receptors, NPFFR1 (NPFF1) and NPFFR2 (NPFF2). Through these receptors it influences several systems:
- Opioid modulation. NPFF dampens the analgesic effect of opioids such as morphine and has been investigated for its role in the development of opioid tolerance.
- Pain processing. Spinal NPFF interacts with μ- and δ-opioid antinociception in ways distinct from cholecystokinin (Neuropeptides 1990, cited in J Med Chem 2006).
- Feeding behavior. In chicks, central NPFF (and the related NPVF) suppresses food intake, in contrast to PrRP and GnIH which stimulate it (Cline et al., cited in Comp Biochem Physiol A 2009).
- Reproductive neurocircuitry. NPFFR1 and NPFFR2 are expressed in brain areas relevant to female sexual behavior, and NPFF receptors have been implicated in kisspeptin-mediated lordosis (Front Endocrinol 2022).
- Cross-talk with other peptide systems. Human kisspeptins can activate the NPFF2 receptor at relevant concentrations (Lyubimov and colleagues, Neuroscience), blurring the receptor selectivity of these RFamide families.
Mechanism
NPFFR1 and NPFFR2 are class A G-protein-coupled receptors. Pharmacological characterization of the human receptors expressed in CHO cells was reported by Bonini and colleagues (Eur J Pharmacol 2002, cited in J Med Chem 2006), confirming that NPFF binds both receptors with nanomolar affinity. Structure-activity work shows that the C-terminal phenylalanine of NPFF is relatively intolerant of substitution, and the C-terminal amide cap is required for receptor engagement (J Med Chem 2006). NPFF is part of a wider cross-reactivity web among RFamide peptides: at higher concentrations kisspeptin-10 has been shown to bind and activate NPFF/GnIH receptor systems (J Clin Endocrinol Metab 2011), and NPFF receptors have been discussed in the context of interactions with the AT2 and MAS receptors (Pharmacol Rev 2014).
Evidence
- Human: Limited. NPFF and its receptors have been studied in human tissue and human-receptor cell systems, but no NPFF-based therapeutic has reached late-stage clinical trials based on the sources in this dossier.
- Animal: Extensive rodent literature on opioid tolerance, antinociception, food intake, and reproductive behavior. Knockout and antagonist studies (e.g., the NPFFR1 antagonist BIBP3226 in lordosis assays) anchor much of the in vivo work.
- In vitro: Receptor pharmacology in heterologous expression systems (CHO cells expressing human NPFFR1/NPFFR2) and competitive binding studies on native tissue established the nanomolar-affinity profile and informed early small-molecule SAR programs (J Med Chem 2006).
Related peptides
NPFF sits inside the broader RFamide superfamily. Related cards on the platform may include kisspeptin, RFRP-3/GnIH, PrRP, and 26RFa/QRFP — all of which share the C-terminal Arg-Phe-NH₂ motif and overlap pharmacologically with the NPFF receptors. Where another RFamide card exists on the platform, it is the natural cross-reference; cards not yet created are listed here as plain text rather than as broken links.
Research directions for this peptide, selected from the current sources — hypotheses you can explore and model. None of it is proven yet; tap any one to see the full thinking.
Does NPFF reduce opioid effects primarily through the spinal NPFFR1 receptor rather than the annotated NPFFR2?
If true, drugs designed to block NPFF's anti-opioid action would need to target NPFFR1, not NPFFR2. This could help scientists design better medicines to prevent opioid tolerance in pain patients.
Could a modified version of NPFF keep only the pain-control effect while leaving heart-rate and blood-pressure effects behind?
Many promising peptide medicines fail because they affect the heart unexpectedly. If NPFF's cardiovascular and pain effects come from different receptors in different locations, drug designers could build a safer version that helps chronic pain patients without risking cardiovascular complications.
Could NPFF reduce neuropathic pain, which opioids barely touch, by also acting on the sigma-1 receptor?
Millions of people with nerve-damage pain get little relief from opioids. If NPFF works through a second mechanism, it could form the basis of a new treatment for conditions like diabetic neuropathy or post-chemotherapy pain.
Does a natural kink in NPFF's shape, caused by one proline amino acid, keep it locked onto pain-related receptors and away from others in its family?
If true, chemists could redesign NPFF with very small changes to steer it toward or away from specific receptors, potentially creating targeted medicines for pain that avoid side effects tied to other members of this peptide family, such as effects on reproductive hormones.
Does the chemical cap at the end of NPFF change the shape of how it sits in its receptor, rather than just making it last longer?
If true, designers of NPFF-based medicines could mimic just that tail-cap interaction to create simpler, more stable compounds, potentially making pain-modulating drugs easier to manufacture and deliver.
If given together with opioids, could NPFF prevent the body from becoming tolerant to pain medicine without reducing how well the medicine works at first?
Opioid tolerance forces doctors to keep raising doses, increasing overdose risk. A drug based on NPFF that slows tolerance could help patients stay on lower, safer opioid doses for longer, benefiting the millions of people managing chronic pain conditions.
▸full evidence table2 metrics
| metric | value | tool |
|---|---|---|
| ipTM | 0.6151586771011353 | openfold3-mlx |
| ranking score | 0.7170758843421936 | openfold3-mlx |
▸structural qualityopenfold3
| metric | value | note |
|---|---|---|
| gpde | 0.508 | global PDE — lower = better |
| disorder | 0.108 | fraction disordered |
| chain pair ipTM (A, B) | 0.615 | interface quality |
▸3-letter notation
▸recipeopenfold3-mlx 0.3.1
| parameter | value |
|---|---|
| model | openfold3-mlx 0.3.1 |
| weights | aedd8f3eb814e392… |
| hardware | apple_m4_base_16gb |
| mlx version | 0.31.1 |
| python | 3.14.3 |
| random seed | 42 |
| msa strategy | colabfold |
| diffusion samples | 1 |
| runtime | 80s |
| predicted by | mlx@peptide |
| predicted at | 2026-05-03 |
python3 openfold3/run_openfold.py predict --query_json {query.json} --runner_yaml examples/example_runner_yamls/mlx_runner.yml --output_dir {output_dir} --num_diffusion_samples 1 ▸citationbibtex
@peptide{pep10803,
sequence = {FLFQPQRF},
target = {npffr2},
author = {peptidemodel},
year = {2026},
status = {bioassayed}
}