Related Experiment Videos
Effect of morphine and naloxone on intestinal transit in mice
Abstract:
Morphine caused a dose-dependent slowing of the rate of intestinal transit in mice. This inhibitory effect of morphine was antagonised by naloxone administration. Pretreatment with a single dose of morphine did not induce any detectable tolerance to the inhibitory effect of a second dose of morphine given 5 h later. However, naloxone was more effective in antagonising this inhibitory effect of morphine in morphine-pretreated mice than in saline-pretreated animals. Molecular sieve morphine pellet implantation for 24 h induced detectable tolerance to the inhibitory effect of morphine administered 3 h after removal of the pellet. In addition, the antagonistic effect of naloxone was also augmented when compared with blank pellet-implanted control animals. The present study has shown that the enhanced naloxone potency against the inhibitory effect of morphine was intestinal transit was observalbe before the development of overt tolerance, and that tolerance to the effect of morphine on the small intestine could be induced by implantation of a molecular sieve morphine pellet for 24 h.
Insights
Morphine slows intestinal transit in mice, an effect blocked by naloxone. Tolerance to morphine
Area of Science:
- Pharmacology
- Gastroenterology
- Neuroscience
Background:
- Opioids like morphine are known to affect gastrointestinal motility.
- Understanding the development of tolerance to opioid-induced constipation is crucial for pain management.
Purpose of the Study:
- To investigate the development of tolerance to morphine's inhibitory effect on intestinal transit in mice.
- To examine the role of naloxone in antagonizing morphine's effects and its interaction with tolerance.
Main Methods:
- Administered morphine to mice to assess dose-dependent effects on intestinal transit.
- Utilized naloxone to antagonize morphine's effects.
- Investigated tolerance development using single-dose pretreatment and chronic morphine pellet implantation.
Main Results:
- Morphine dose-dependently slowed intestinal transit, an effect reversed by naloxone.
- Short-term morphine pretreatment did not induce significant tolerance.
- Chronic morphine pellet implantation induced tolerance to morphine's inhibitory effects on intestinal transit.
- Naloxone's antagonistic potency was enhanced in morphine-tolerant mice.
Conclusions:
- Enhanced naloxone potency against morphine's effects on intestinal transit can precede overt tolerance.
- Chronic morphine pellet implantation is an effective method for inducing tolerance to morphine's effects on the small intestine.