title: Neural control of the sphincter of Oddi. Physiologic role of enkephalins on the regulation of basal sphincter of Oddi motor activity in the cat.
abstract: The effect and physiologic role of enkephalins on the sphincter of Oddi was studied in the cat. Leucine- and methionine-enkephalin caused an initial sphincter of Oddi contraction followed by a more prolonged relaxation. The excitatory effect of leucine-enkephalin was antagonized partially by atropine and by methysergide infusion. It was completely blocked by a combination of atropine and methysergide infusion, by tetrodotoxin, by 5-hydroxytryptamine depletion induced by reserpine, and by 5-hydroxytryptamine tachyphylaxis. Naloxone infusion decreased sphincter of Oddi motor activity, which was reversed by tetrodotoxin. Maximal sphincter of Oddi relaxation was induced by doses of naloxone (40 micrograms/kg) that antagonized a maximal dose of morphine. Higher doses of naloxone (640 micrograms/kg) were needed to block maximal doses of enkephalin (8 micrograms/kg). The enkephalin inhibitory action was blocked only by tetrodotoxin. These findings indicate that (a) leucine-enkephalin has two receptor sites on the sphincter of Oddi--one at the serotonergic neurons and the other at noncholinergic, nonadrenergic inhibitory neurons, and (b) opioid peptides participate in the intramural excitatory pathway to the sphincter of Oddi.
mesh_terms: D014670:Ampulla of Vater / Q000502:physiology*; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001340:Autonomic Nerve Block; D002415:Cats; D004743:Enkephalin, Leucine / Q000502:physiology; D004744:Enkephalin, Methionine / Q000502:physiology; D004745:Enkephalins / Q000008:administration & dosage / Q000502:physiology*; D005260:Female; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D012110:Reserpine / Q000494:pharmacology; D012701:Serotonin; D012702:Serotonin Antagonists; D009803:Sphincter of Oddi / Q000502:physiology*; D013779:Tetrodotoxin
chemical_list: D004745:Enkephalins; D012702:Serotonin Antagonists; D012701:Serotonin; D013779:Tetrodotoxin; D004744:Enkephalin, Methionine; D004743:Enkephalin, Leucine; D001285:Atropine; D012110:Reserpine