AJP - Gastrointestinal and Liver Physiology, Vol 249, Issue 5 557-G562, Copyright © 1985 by American Physiological Society
Morphine initiates migrating myoelectric complexes by acting on peripheral opioid receptors
G. L. Telford, M. Hoshmonai, A. J. Moses and J. H. Szurszewski
The role of peripheral and central opioid receptors in morphine-induced
migrating myoelectric complexes (MMECs) was studied in conscious dogs
implanted with silver-silver chloride electrodes. In normal fasted dogs
morphine (100-200 micrograms/kg iv) initiated phase III of the MMEC in the
duodenum. Once initiated the MMEC propagated distally. This effect of
morphine was blocked by the opioid receptor antagonists naloxone (2 mg/kg
iv) and N,N-diallylnormorphinium bromide (4 mg/kg iv). Higher doses of
morphine (300-600 micrograms/kg iv) initiated phase III activity in fed
dogs as early as 20 min after feeding, while lower doses (150 micrograms/kg
iv) initiated phase III activity routinely when administered 100 min after
feeding. In dogs with bilateral vagotomies and bilateral thoracolumbar
sympathetic chain ganglionectomies, morphine (150 micrograms/kg iv)
initiated phase III activity in the duodenum, which then migrated distally.
This study demonstrates that morphine initiates phase III of the MMEC by
acting through peripheral opioid receptors.
