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Evidence: LowPeptideResearch ChemicalEndogenous opioidNot a drugKappa receptor

Dynorphin

The opioid peptide whose own effects are unpleasant, which is why the drugs built around it are blockers

Dynorphins are opioid peptides cut from prodynorphin that act mainly at kappa-opioid receptors. Unlike the other endogenous opioids they produce dysphoria rather than pleasure, so the therapeutic interest is in blocking them, not giving them.

At a Glance Read Research →
Overview

What is it?

Dynorphins come from the precursor prodynorphin and prefer kappa-opioid receptors, though they bind all three major opioid receptor types. Some of their effects survive blockade by naloxone and by removal of the opioid-recognition tyrosine, which is why parts of their pharmacology are called non-opioid.

The kappa system is studied as the stress and aversion arm of the opioid network: reviews describe the dynorphin-kappa system working with corticotropin-releasing factor to produce dysphoria, to strengthen drug-seeking, and to reinstate it after stress. That is the opposite of a desirable drug effect, and it is why development has gone toward kappa antagonists.

Human work on dynorphin is measurement rather than treatment. Levels have been examined in brain tissue after death in Alzheimer's disease, and in plasma. The one study that gave it to people did so to validate a laboratory assay in two subjects.

Structured data

At a Glance

Every value in this table is printed from the Grey Peptides dataset, the same record the compound explorer and comparison tool read, so the three can never disagree.

ClassDynorphin is the endogenous kappa-opioid receptor agonist — unlike the euphoria-producing beta-endorphin and enkephalins, dynorphin produces dysphoria and aversion, serving as the brain's 'anti-reward' signal.
SequenceYGGFLRRIRPKLKWDNQ (Dynorphin A 1-17)
FormulaC99H155N31O23
Molecular weight2147.5 g/mol
Half-lifenot reported in the sources read
US statusResearch Chemical
Evidence levelLow
Last reviewed2026-10-01
Evidence

Published Research

These are the studies in people, read from their PubMed abstracts: two measurement studies, one assay study and two reviews.

Human2007

Raised in Alzheimer's brain tissue

In post-mortem samples, people with Alzheimer's disease had robustly higher dynorphin A than controls, with no difference in dynorphin B or nociceptin. Samples from Parkinson's disease and cerebrovascular disease did not differ from controls.

PMID: 16914231
Human1997

Infused, to test an assay

A chromatography and radioimmunoassay method for dynorphin A1-13 and its metabolites reached a detection limit of 0.07 ng/mL, and was applied to blood from two subjects given intravenous infusions of 250 or 1,000 micrograms per kilogram over ten minutes.

PMID: 9447557
Human1998

Measured in plasma

In human plasma, dynorphin A was rapidly converted by proteases while dynorphin B was not; basal dynorphin B was about 1 fmol/mL and beta-endorphin about 16 fmol/mL in 11 men.

PMID: 9809646
Review2010

Why the drugs are blockers

A review of the dynorphin and kappa-opioid system as a driver of stress-induced and pro-addictive behaviour, working alongside corticotropin-releasing factor to produce dysphoria, strengthen drug seeking and reinstate it after stress.

PMID: 19716811
Review1988

The pharmacology, including what naloxone does not block

A review of dynorphin pharmacology: binding at mu, delta and kappa receptors with a preference for kappa, plus effects that persist without the opioid-recognition tyrosine or in the presence of naloxone, which are described as non-opioid.

PMID: 2898233
Safety

Side Effects & Contraindications

Reported Side Effects

Almost nobody has been given it; the effects below come from the receptor it acts on.

● Kappa-opioid activation produces dysphoria, which is the system's defining feature in the reviews
● The one human infusion study reported no effects, because it was measuring an assay in two subjects
● Nothing is established about repeated dosing in people

Contraindications & Cautions

Not a medicine.

● Any use outside a supervised research study
● It is an opioid agonist; its own effects are the ones drug development is trying to block
Questions

Frequently Asked Questions

?What are dynorphins?

Opioid peptides cut from prodynorphin that act mainly at kappa-opioid receptors. Dynorphin A and B are the main forms.

?Why do they feel bad rather than good?

They act at kappa receptors, which produce dysphoria rather than euphoria. Reviews describe the system as a driver of stress-induced and addiction-related behaviour.

?Are there drugs based on dynorphin?

The development is in the opposite direction: kappa-opioid antagonists, which block this system, are being tested in depression.

?Has dynorphin been given to people?

Barely. The study we found infused it into two subjects to validate a laboratory assay, not to test an effect.

Bibliography

References

  1. [pubmed] Yakovleva T, et al. "Dysregulation of dynorphins in Alzheimer disease." Neurobiol Aging, 2007;28(11):1700-8. PMID: 16914231.
  2. [pubmed] Müller S, et al. "An HPLC/RIA method for dynorphin A1-13 and its main metabolites in human blood." J Pharm Biomed Anal, 1997;16(1):101-9. PMID: 9447557.
  3. [pubmed] Silberring J, et al. "Characterization of immunoreactive dynorphin B and beta-endorphin in human plasma." Peptides, 1998;19(8):1329-37. PMID: 9809646.
  4. [pubmed] Bruchas MR, et al. "The dynorphin/kappa opioid system as a modulator of stress-induced and pro-addictive behaviors." Brain Res, 2010;1314:44-55. PMID: 19716811.
  5. [pubmed] Smith AP, et al. "Pharmacology of dynorphin." Annu Rev Pharmacol Toxicol, 1988;28:123-40. PMID: 2898233.
  6. [pubmed] Goldstein A, et al. "Dynorphin-(1-13), an extraordinarily potent opioid peptide." Proc Natl Acad Sci U S A, 1979;76(12):6666-70. PMID: 230519.

Sources & Citations

Studies were read from their PubMed abstracts on October 1, 2026; the US status was checked in Drugs@FDA the same day.

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. Consult a licensed healthcare provider before making health decisions.

Last reviewed: 2026-10-01