Big Dynorphin Causes Pain Through NMDA Receptors, Not Opioid Receptors
Big dynorphin (a large opioid peptide precursor) caused pain and neurological symptoms when injected spinally, working through NMDA glutamate receptors rather than opioid receptors — an opioid peptide causing pain through a non-opioid mechanism.
Quick Facts
What This Study Found
Intrathecal big dynorphin at femtomole doses caused nociceptive behavior through NMDA receptor activation (blocked by MK-801) but not through opioid receptors (not blocked by naloxone), with higher doses causing reversible paralysis.
Key Numbers
How They Did This
Animal study in mice with intrathecal injection of big dynorphin at graded doses. Pain behavior and paralysis assessed. MK-801 (NMDA antagonist) and naloxone (opioid antagonist) used to dissect mechanisms.
Why This Research Matters
In chronic pain conditions where dynorphin is elevated, big dynorphin may paradoxically CAUSE pain through NMDA receptors — explaining the pain-promoting role of dynorphin in some chronic pain states.
The Bigger Picture
The same opioid system that normally controls pain can paradoxically promote it. Big dynorphin's NMDA-mediated pain causation helps explain why some chronic pain patients have elevated dynorphin yet still experience pain.
What This Study Doesn't Tell Us
Mouse study with intrathecal injection of a precursor peptide at extremely low doses. The physiological relevance of big dynorphin at these spinal concentrations is uncertain.
Questions This Raises
- ?Does elevated spinal big dynorphin contribute to chronic pain syndromes?
- ?Could NMDA antagonists targeted at dynorphin's site of action relieve specific chronic pain types?
- ?Is big dynorphin processing disrupted in chronic pain?
Trust & Context
- Key Stat:
- Opioid causes pain Big dynorphin caused pain through NMDA glutamate receptors, NOT opioid receptors — explaining the paradox of elevated dynorphin in painful conditions
- Evidence Grade:
- Preliminary animal evidence with clear pharmacological dissection (MK-801 blocks, naloxone doesn't) identifying an unexpected non-opioid mechanism.
- Study Age:
- Published in 2002. Big dynorphin's pronociceptive role through NMDA receptors has been confirmed and is now a recognized mechanism in chronic pain pathophysiology.
- Original Title:
- Intrathecally administered big dynorphin, a prodynorphin-derived peptide, produces nociceptive behavior through an N-methyl-D-aspartate receptor mechanism.
- Published In:
- Brain research, 952(1), 7-14 (2002)
- Authors:
- Tan-No, Koichi, Esashi, Akihisa, Nakagawasai, Osamu, Niijima, Fukie, Tadano, Takeshi, Sakurada, Chikai, Sakurada, Tsukasa, Bakalkin, Georgy, Terenius, Lars, Kisara, Kensuke
- Database ID:
- RPEP-00778
Evidence Hierarchy
Tests effects in animals (usually mice or rats), not humans.
What do these levels mean? →Frequently Asked Questions
Can the body's own opioids cause pain?
Yes. Big dynorphin, a large opioid peptide, caused pain when it accumulated in the spinal cord — but NOT through opioid receptors. It activated NMDA glutamate receptors, which cause excitotoxic pain.
Why does this matter for chronic pain?
In chronic pain, dynorphin levels rise in the spinal cord. Instead of helping with pain (through opioid receptors), big dynorphin may actually be making pain worse through NMDA receptors. This explains why opioid drugs don't help some chronic pain patients.
Read More on RethinkPeptides
Cite This Study
https://rethinkpeptides.com/research/RPEP-00778APA
Tan-No, Koichi; Esashi, Akihisa; Nakagawasai, Osamu; Niijima, Fukie; Tadano, Takeshi; Sakurada, Chikai; Sakurada, Tsukasa; Bakalkin, Georgy; Terenius, Lars; Kisara, Kensuke. (2002). Intrathecally administered big dynorphin, a prodynorphin-derived peptide, produces nociceptive behavior through an N-methyl-D-aspartate receptor mechanism.. Brain research, 952(1), 7-14.
MLA
Tan-No, Koichi, et al. "Intrathecally administered big dynorphin, a prodynorphin-derived peptide, produces nociceptive behavior through an N-methyl-D-aspartate receptor mechanism.." Brain research, 2002.
RethinkPeptides
RethinkPeptides Research Database. "Intrathecally administered big dynorphin, a prodynorphin-der..." RPEP-00778. Retrieved from https://rethinkpeptides.com/research/tan-no-2002-intrathecally-administered-big-dynorphin
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkPeptides research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.