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Morphine versus motilin in the initiation of migrating myoelectric complexes
Abstract:
The roles of morphine and motilin in the initiation of migrating myoelectric complex (MMC) cycles were studied in four conscious dogs. Morphine or motilin boluses and morphine or motilin infusions were administered to healthy conscious dogs, each implanted with a set of 12 electrodes on the small intestine. The durations of premature phase IIIs initiated by morphine and motilin were not significantly different from each other or from control values. The premature phase IIIs initiated by morphine boluses propagated significantly faster over the 1st half of small intestine than the control or motilin bolus-initiated phase IIIs. The latent period for the onset of phase IIIs after morphine was not significantly different from that after motilin. Morphine infusion (50 micrograms X kg-1 X h-1) generally initiated one or two premature MMC cycles and then disrupted further MMC cycling. Motilin infusion (0.3 microgram X kg-1 X h-1) initiated one premature MMC cycle, and then further cycling continued at the normal rate. We conclude that morphine acts on both the MMC-initiating and MMC-propagating mechanisms, whereas motilin acts only on the MMC-initiating mechanism. Morphine has both excitatory and disruptive effects on MMC cycling, while motilin has only excitatory effects.
Insights
Morphine and motilin initiate migrating myoelectric complex (MMC) cycles. Morphine also speeds up MMC propagation and can disrupt cycling, while motilin only initiates and excites MMC activity.
Area of Science:
- Gastroenterology
- Neurogastroenterology
- Pharmacology
Background:
- The migrating myoelectric complex (MMC) is crucial for gut motility.
- Understanding the regulation of MMC initiation is vital for treating motility disorders.
Purpose of the Study:
- To investigate the distinct roles of morphine and motilin in initiating and propagating migrating myoelectric complex (MMC) cycles.
- To differentiate the effects of morphine and motilin on MMC activity.
Main Methods:
- Administered morphine and motilin via bolus and infusion to conscious dogs with implanted intestinal electrodes.
- Monitored and analyzed the initiation, duration, latency, and propagation of MMC phase IIIs.
Main Results:
- Both morphine and motilin initiated premature phase IIIs with similar durations and latent periods.
- Morphine boluses significantly increased the propagation speed of phase IIIs compared to motilin or controls.
- Morphine infusion disrupted subsequent MMC cycling, whereas motilin infusion allowed normal cycling to resume.
Conclusions:
- Morphine influences both MMC initiation and propagation, exhibiting excitatory and disruptive effects.
- Motilin primarily acts on MMC initiation, showing only excitatory effects on MMC cycling.