Morphine initiates migrating myoelectric complexes by acting on peripheral opioid receptors.
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.
D000818:Animals; D001696:Biomechanical Phenomena; D003714:Denervation; D004064:Digestive System / Q000187:drug effects*; D004285:Dogs; D004435:Eating; D004594:Electrophysiology; D005215:Fasting; D005769:Gastrointestinal Motility / Q000187:drug effects; D007421:Intestine, Small / Q000294:innervation; D009020:Morphine / Q000494:pharmacology*; D011957:Receptors, Opioid / Q000187:drug effects*; D013270:Stomach / Q000294:innervation
D011957:Receptors, Opioid; D009020:Morphine