title: Opioid receptors of bovine posterior pituitary neurosecretosomes are exclusively kappa.
abstract: Intact neurosecretosomes (NSS) from bovine posterior pituitary were prepared and characterized. Ligand binding studies were performed, using 3H-[D-Ala2-D-Leu5]enkephalin (DADL), 3H-etorphine and 3H-ethylketocyclazocine (EKC). The absence of specific binding of 3H-DADL and the inability of DADL to displace 3H-etorphine, implies the absence of mu, delta, or DADL-suppressible benzomorphan ("kappa-2") sites. Self- and cross displacement studies for etorphine and EKC suggested receptor heterogeneity. EKC fails to displace - 20% of specific binding of etorphine. Mathematical modelling indicates the presence of three classes of sites. The present findings imply that bovine posterior pituitary opioid receptors are exclusively of the kappa type.
mesh_terms: D000701:Analgesics, Opioid / Q000494:pharmacology; D000818:Animals; D002417:Cattle; D003496:Cyclazocine / Q000031:analogs & derivatives / Q000494:pharmacology; D003594:Cytoplasmic Granules / Q000378:metabolism*; D004743:Enkephalin, Leucine / Q000031:analogs & derivatives / Q000494:pharmacology; D016308:Enkephalin, Leucine-2-Alanine; D016314:Ethylketocyclazocine; D005048:Etorphine / Q000378:metabolism*; D007700:Kinetics; D009019:Morphinans / Q000378:metabolism*; D010904:Pituitary Gland, Posterior / Q000378:metabolism*; D011957:Receptors, Opioid / Q000378:metabolism*; D017473:Receptors, Opioid, kappa
chemical_list: D000701:Analgesics, Opioid; D009019:Morphinans; D011957:Receptors, Opioid; D017473:Receptors, Opioid, kappa; D005048:Etorphine; D016314:Ethylketocyclazocine; D004743:Enkephalin, Leucine; D016308:Enkephalin, Leucine-2-Alanine; D003496:Cyclazocine