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Morphine induces delayed anorexia in rats
1Psychology Department, University of Haifa, Israel.
Psychopharmacology
|January 1, 1988
Summary
Morphine causes a delayed anorexia in rats, characterized by a persistent decrease in feeding lasting up to 24 hours. This effect is partially reversible with naltrexone, indicating opioid receptor involvement in feeding regulation.
Area of Science:
- Neuroscience
- Pharmacology
- Behavioral Science
Background:
- Opioid agonists like morphine are known to affect feeding behavior.
- The precise temporal profile and underlying mechanisms of morphine-induced feeding suppression require further elucidation.
Purpose of the Study:
- To investigate the delayed anorexic effects of morphine in a rat model.
- To characterize the triphasic influence of morphine on feeding patterns.
- To explore the involvement of opioid receptors in delayed morphine-induced anorexia.
Main Methods:
- Rats were administered a single injection of morphine.
- Feeding behavior was monitored over a 24-hour period.
- The effects of naltrexone, an opioid antagonist, were assessed on morphine-induced anorexia.
Main Results:
- Morphine induced a triphasic feeding response: initial anorexia, followed by hyperphagia, and a persistent delayed anorexia (4-24 h).
- The delayed anorexic effect was partially reversible by naltrexone, with antagonism lasting longer than naltrexone's direct effect.
- Delayed anorexia was independent of initial stupor, feeding status, or gastric distension.
Conclusions:
- Morphine exerts a complex, time-dependent influence on feeding behavior in rats.
- A distinct, delayed anorexic effect mediated by opioid receptors is evident.
- These findings contribute to understanding opioid-related feeding modulation and have implications for appetite regulation research.