Colonic motor responses in the pony: relevance of colonic stimulation by opiate antagonists.
Abstract: The electrical and mechanical activity of the digestive tract and its response to the administration of opiate agonists and antagonists was assessed from electrodes and strain gauges chronically implanted on the jejunum and the cecocolonic segments in 3 ponies given a diet of hay and concentrates. Before the drugs were given, 10 to 17 migrating myoelectric complexes/day were recorded on the small intestine, and a rhythmic motor activity (base line) was observed on the proximal portion of the colon at the rate of 3.5 to 6.6/hour. Propagated contractions from the proximal to the distal portion of the colon occurred at the rate of 1.5 to 2.3/hour. Each pony was used as its own control and was given morphine (0.5 or 1 mg/kg of body weight, IV) or fentanyl (0.01 or 0.05 mg, IV) at weekly intervals. After an early phase of inhibition of the overall activity that lasted from 0.5 to 3 hours, depending on the dose, the resting muscle tone of the colonic activity was increased for a dose-dependent period. Propagated contractions only reappeared at the end of this 2nd phase. The opiate antagonist naloxone (0.5 mg/kg, IV) elicited a marked propulsive activity on the left replicated colonic segment, characterized by an increase in the number of propagated contractions. The N-methyl-quaternary analog of naloxone (methylnaloxone, which presumably entails selective action at opiate receptors outside the CNS) was also effective, indicating peripheral effects at the dosage level used (0.5 mg/kg, IV). Seemingly, an inhibitory opioid system exists in the control of colonic motor function in ponies and the possible usefulness of opiate antagonists to relieve hypomotility resulting in colonic impaction and constipation.
Publication Date: 1985-01-01 PubMed ID: 3970439
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- Journal Article
Summary
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This research study explores how the application of opiate antagonists affects the motor activity of the colon in ponies, suggesting potential medicinal benefits in managing conditions such as constipation and colonic impaction.
Study Setup
- The study involved three ponies that were administered with a diet of hay and concentrates. Instruments were inserted into the animals’ digestive tracts to record their electrical and mechanical activity.
- The jejunum (part of the small intestine) and cecocolonic segments (a section of the colon) were monitored for activity frequency and intensity.
- Baseline daily averages for activity were established before the administration of drugs.
The Effects of Opiate Agonists
- The ponies were given morphine or fentanyl at varying doses, on a weekly interval basis.
- Following the administration of these drugs, there was an initial period of reduced activity lasting from 0.5 to 3 hours, depending on the dosage.
- After this initial phase, an increased resting muscle tone of colonic activity was observed for a period which directly correlated to the drug’s dosage.
- It should be noted that the occurrence of propogated contractions was noticeably reestablished only at the end of this phase.
The Effects of Opiate Antagonists
- The study also looked at the effects of naloxone, an opiate antagonist, on the digestive tract. The post-drug phase proved that naloxone generated a significant propulsive activity on the replicated colonic segment.
- This effect was characterized by an increase in the number of propagated contractions.
- A N-methyl-quaternary analog of naloxone, methylnaloxone, was used, which is reportedly acting selectively on opiate receptors outside the central nervous system. The same dosage as naloxone resulted in similar effects.
Overall Implications
- The findings suggest the existence of an inhibitory opioid system regulating colonic motor function in ponies.
- This could point towards the potential use of opiate antagonists in treating disorders associated with low gut motility, such as colonic impaction and constipation.
Cite This Article
APA
Roger T, Bardon T, Ruckebusch Y.
(1985).
Colonic motor responses in the pony: relevance of colonic stimulation by opiate antagonists.
Am J Vet Res, 46(1), 31-35.
Publication
Researcher Affiliations
MeSH Terms
- Animals
- Colon / drug effects
- Electromyography / veterinary
- Fentanyl / pharmacology
- Horses / physiology
- Morphine / pharmacology
- Muscle Contraction / drug effects
- Muscle Tonus / drug effects
- Muscle, Smooth / drug effects
- Naloxone / pharmacology
- Narcotic Antagonists / pharmacology
- Oxymorphone / pharmacology
Citations
This article has been cited 1 times.- Roger T, Bardon T, Ruckebusch Y. Comparative effects of mu and kappa opiate agonists on the cecocolic motility in the pony.. Can J Vet Res 1994 Jul;58(3):163-6.
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