title: Characterization of specific delta-opioid binding sites in the distal small intestine of swine.
abstract: Delta-opioid receptors modulate neurogenic smooth muscle contractions and mucosal ion transport in the porcine distal small intestine. We compared specific delta-opioid binding sites in neuronal membranes isolated from the inner submucosal plexus and myenteric plexus of this gut region. In both preparations, the delta-opioid receptor antagonist naltrindole displaced [3H]diprenorphine from two binding sites. [3H]Naltrindole bound specifically to a single high-affinity site that was displaced by delta-opioid receptor ligands with the rank order of affinity: naltriben >7-benzylidenenaltrexone>deltorphin II>[D-Pen(2), D-Pen(5)] enkephalin. Relative decreases in delta-opioid receptor agonist affinity in the presence of Na(+) and other ions differed in submucosal and myenteric membranes. The kappa-opioid receptor antagonist norbinaltorphimine displaced [3H]naltrindole binding in myenteric membranes (K(i)=7.2 nM). Delta-opioid receptors in submucosal and myenteric plexuses of porcine ileum appear to differ in some respects.
authors.affiliation: Department of Veterinary PathoBiology, College of Veterinary Medicine, University of Minnesota, 1988 Fitch Avenue, St. Paul, MN 55108-6010, USA.
authors.forename: DeWayne
authors.initials: D
authors.lastname: Townsend
authors.forename: David R
authors.initials: DR
authors.lastname: Brown
mesh_terms: D000818:Animals; D001665:Binding Sites / Q000187:drug effects / Q000502:physiology; D005260:Female; D007421:Intestine, Small / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009292:Narcotic Antagonists / Q000378:metabolism / Q000494:pharmacology; D017465:Receptors, Opioid, delta / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013552:Swine
chemical_list: D009292:Narcotic Antagonists; D017465:Receptors, Opioid, delta