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Morphine initiates migrating myoelectric complexes by acting on peripheral opioid receptors

G L Telford, M Hoshmonai, A J Moses

    The American Journal of Physiology
    |November 1, 1985
    PubMed

    Insights

    Morphine triggers gut contractions, known as migrating myoelectric complexes (MMECs), by acting on peripheral opioid receptors. This effect was observed in dogs and could be blocked by opioid antagonists.

    Area of Science:

    • Gastroenterology
    • Pharmacology
    • Neuroscience

    Background:

    • Morphine is known to affect gastrointestinal motility.
    • Migrating myoelectric complexes (MMECs) are important for gut clearance.
    • The specific receptors involved in morphine's effect on MMECs are not fully understood.

    Purpose of the Study:

    • To investigate the role of peripheral and central opioid receptors in morphine-induced MMECs.
    • To determine the site of action for morphine's effect on the initiation of phase III of the MMEC.

    Main Methods:

    • Conscious dogs were surgically implanted with electrodes to record myoelectric activity.
    • Morphine was administered intravenously at various doses to fasted and fed dogs.
    • Opioid receptor antagonists (naloxone and N,N-diallylnormorphinium bromide) were used to block morphine's effects.
    • Studies were conducted in dogs with vagotomies and sympathetic denervation.

    Main Results:

    • Morphine initiated phase III of the MMEC in the duodenum, which then propagated distally.
    • The effect of morphine was blocked by opioid receptor antagonists.
    • Morphine induced phase III activity in both fasted and fed states, with dose and timing adjustments.
    • Morphine's effect persisted even after vagotomies and sympathetic denervation.

    Conclusions:

    • Morphine initiates phase III of the migrating myoelectric complex (MMEC) by acting through peripheral opioid receptors.
    • Central opioid receptors are not essential for morphine-induced MMEC initiation.
    • These findings clarify the peripheral mechanism of morphine's prokinetic effect on the gastrointestinal tract.

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