title: Benzomorphan sites are ligand recognition sites of putative epsilon-receptors.
abstract: The binding characteristics of benzomorphan sites of rat brain membranes are compared with those of kappa-sites of human placenta and guinea pig brain membranes. Enkephalins and the stable analog [D-Ala2,D-Leu5]enkephalin, which are virtually inactive at kappa-sites, possess moderate binding affinity at benzomorphan sites. In contrast, a dynorphin analog, PL017-dynorphin A(6-17), binds well to kappa-sites but poorly to benzomorphan sites. Among all opioid peptides tested, beta h-endorphin, which is essentially inactive at the kappa-receptor sites, is the most potent ligand at benzomorphan sites. The potencies of beta h-endorphin and its fragments at epsilon-receptors of the rat vas deferens correlate well with their binding affinities of benzomorphan sites but not of mu- and delta-sites. These data, as well as the data which show the distinct distribution of benzomorphan sites in rat brain as compared with the distribution of mu- and delta-sites of rat brain and of kappa-sites of guinea pig brain, suggest that benzomorphan sites of rat brain are the ligand-binding sites of epsilon-receptors.
mesh_terms: D000818:Animals; D001575:Benzomorphans / Q000378:metabolism*; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D004174:Diprenorphine / Q000378:metabolism; D004399:Dynorphins / Q000031:analogs & derivatives / Q000378:metabolism; D004723:Endorphins / Q000378:metabolism; D004743:Enkephalin, Leucine / Q000031:analogs & derivatives / Q000378:metabolism; D016308:Enkephalin, Leucine-2-Alanine; D005260:Female; D006168:Guinea Pigs; D006801:Humans; D007700:Kinetics; D009019:Morphinans / Q000378:metabolism*; D010446:Peptide Fragments; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy; D051381:Rats; D011957:Receptors, Opioid / Q000378:metabolism*; D017473:Receptors, Opioid, kappa; D001615:beta-Endorphin
chemical_list: D001575:Benzomorphans; D004723:Endorphins; D009019:Morphinans; C043467:PL017-dynorphin A (6-17); D010446:Peptide Fragments; D011957:Receptors, Opioid; D017473:Receptors, Opioid, kappa; C042237:benzomorphan receptor; C043460:epsilon receptor; D004174:Diprenorphine; D004743:Enkephalin, Leucine; D001615:beta-Endorphin; D016308:Enkephalin, Leucine-2-Alanine; D004399:Dynorphins