Dynorphin Injected Into the Brain Triggers Rapid Eating in Pigs
Full-length dynorphin injected into pig brains triggered feeding within 2-5 minutes and increased meal size, while naloxone (an opioid blocker) reduced food intake — confirming opioid peptides drive appetite.
Quick Facts
What This Study Found
Full-length dynorphin A (1-17 or 1-13), leumorphin, and alpha-neo-endorphin induced rapid feeding in pigs. Shorter fragments were ineffective. Naloxone blocked all feeding effects.
Key Numbers
How They Did This
Pigs with lateral ventricle cannulas received 200 µg injections of various opioid peptides. Food intake was measured using operant feeding panels with ad lib food and water.
Why This Research Matters
Pigs are closer to humans than rodents in body size and feeding behavior. Demonstrating opioid-driven feeding in pigs strengthens the case that opioid peptides regulate human appetite.
The Bigger Picture
This study used pigs — which are physiologically closer to humans than rodents — to demonstrate that opioid peptides regulate appetite. This connection between the opioid system and eating behavior helps explain why opioid medications affect appetite and why naltrexone (a clinical opioid blocker) is used in weight management medications.
What This Study Doesn't Tell Us
Brain injections of 200 µg are pharmacological, not physiological doses. The study used young pigs. Human feeding behavior involves many additional psychological and social factors.
Questions This Raises
- ?Could kappa opioid receptor antagonists help reduce overeating in humans?
- ?Why does the full-length dynorphin peptide work while shorter fragments do not?
Trust & Context
- Key Stat:
- Feeding within 2-5 minutes Full-length dynorphin A(1-17) injected into the brain triggered rapid meal initiation in pigs
- Evidence Grade:
- Preliminary animal study using pharmacological (supra-physiological) brain injections. Pigs are a more translatable model than rodents but doses were far above natural levels.
- Study Age:
- Published in 1990. The opioid system's role in appetite has been extensively confirmed, leading to clinical applications like naltrexone-bupropion (Contrave) for weight management.
- Original Title:
- Effects of intracerebroventricular injection of dynorphin, leumorphin and alpha neo-endorphin on operant feeding in pigs.
- Published In:
- Physiology & behavior, 48(6), 821-4 (1990)
- Authors:
- Baldwin, B A, de la Riva, C, Ebenezer, I S
- Database ID:
- RPEP-00146
Evidence Hierarchy
Tests effects in animals (usually mice or rats), not humans.
What do these levels mean? →Frequently Asked Questions
Why do opioid peptides make you hungry?
Opioid peptides like dynorphin activate reward circuits in the brain that make food more pleasurable and increase motivation to eat. This is why opioid medications can increase appetite and why naltrexone can help reduce overeating.
Why are pigs better than rats for studying eating behavior?
Pigs are omnivores with digestive systems and body sizes closer to humans. Their feeding patterns and metabolic responses are more similar to ours than those of small rodents, making findings more translatable.
Read More on RethinkPeptides
Cite This Study
https://rethinkpeptides.com/research/RPEP-00146APA
Baldwin, B A; de la Riva, C; Ebenezer, I S. (1990). Effects of intracerebroventricular injection of dynorphin, leumorphin and alpha neo-endorphin on operant feeding in pigs.. Physiology & behavior, 48(6), 821-4.
MLA
Baldwin, B A, et al. "Effects of intracerebroventricular injection of dynorphin, leumorphin and alpha neo-endorphin on operant feeding in pigs.." Physiology & behavior, 1990.
RethinkPeptides
RethinkPeptides Research Database. "Effects of intracerebroventricular injection of dynorphin, l..." RPEP-00146. Retrieved from https://rethinkpeptides.com/research/baldwin-1990-effects-of-intracerebroventricular-injection
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.