Opioid Peptides Continuously Hold Up Blood Pressure Through the Brainstem
Endogenous opioid peptides in the caudal ventrolateral medulla tonically inhibit blood-pressure-lowering neurons through delta and kappa receptors — a constant opioid contribution to maintaining normal blood pressure.
Quick Facts
What This Study Found
Naloxone injection into the caudal ventrolateral medulla caused dose-dependent blood pressure drops. Delta and kappa receptor antagonists reproduced this effect; mu antagonist did not.
Key Numbers
How They Did This
Anesthetized rabbits received bilateral microinjections of opioid antagonists (naloxone, ICI 174864, nor-binaltorphimine, beta-funaltrexamine) into the caudal ventrolateral medulla. Blood pressure and heart rate were continuously monitored.
Why This Research Matters
This study reveals that the body's natural opioid peptides play a constant role in maintaining blood pressure through the brain. This could be relevant to understanding blood pressure disorders.
The Bigger Picture
Blood pressure regulation is continuous and involves multiple brainstem systems. The finding that opioid peptides constantly restrain the depressor system adds an important piece to the blood pressure puzzle and is relevant to understanding hypotension and blood pressure instability.
What This Study Doesn't Tell Us
Animal study in anesthetized rabbits. Anesthesia itself affects blood pressure regulation. Results may differ in conscious animals or humans.
Questions This Raises
- ?Is this tonic opioid suppression altered in hypotensive disorders?
- ?Could dysfunction of this system contribute to orthostatic hypotension?
Trust & Context
- Key Stat:
- Tonic opioid restraint of depressor neurons Blocking brainstem opioid receptors caused blood pressure to drop, revealing constant opioid suppression of the depressor system
- Evidence Grade:
- Preliminary animal study in anesthetized rabbits. Demonstrates a tonic mechanism but anesthesia may alter baseline activity.
- Study Age:
- Published in 1991. The role of brainstem opioid systems in cardiovascular regulation is now well-established.
- Original Title:
- Endogenous opioids tonically inhibit the depressor neurones in the caudal ventrolateral medulla of rabbits: mediation through delta- and kappa-receptors.
- Published In:
- Neuropharmacology, 30(4), 383-90 (1991)
- Authors:
- Drolet, G, Morilak, D A, Chalmers, J
- Database ID:
- RPEP-00192
Evidence Hierarchy
Tests effects in animals (usually mice or rats), not humans.
What do these levels mean? →Frequently Asked Questions
What does tonic inhibition mean?
It means opioid peptides are constantly active in this brain region, continuously holding back the blood-pressure-lowering neurons. It's not an on-off signal — it's always on, keeping blood pressure from dropping too low.
Why delta and kappa but not mu?
Different opioid receptor types serve different functions even in nearby brain regions. In this particular brainstem area, delta and kappa receptors mediate the tonic cardiovascular regulation, while mu receptors serve other functions or are less abundant.
Read More on RethinkPeptides
Cite This Study
https://rethinkpeptides.com/research/RPEP-00192APA
Drolet, G; Morilak, D A; Chalmers, J. (1991). Endogenous opioids tonically inhibit the depressor neurones in the caudal ventrolateral medulla of rabbits: mediation through delta- and kappa-receptors.. Neuropharmacology, 30(4), 383-90.
MLA
Drolet, G, et al. "Endogenous opioids tonically inhibit the depressor neurones in the caudal ventrolateral medulla of rabbits: mediation through delta- and kappa-receptors.." Neuropharmacology, 1991.
RethinkPeptides
RethinkPeptides Research Database. "Endogenous opioids tonically inhibit the depressor neurones ..." RPEP-00192. Retrieved from https://rethinkpeptides.com/research/drolet-1991-endogenous-opioids-tonically-inhibit
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.