title: The opioid receptor binding of dezocine, morphine, fentanyl, butorphanol and nalbuphine.
abstract: The ability of morphine, fentanyl, butorphanol, nalbuphine, and dezocine to compete with radiolabeled ligands for binding at the mu1, mu2, kappa1, and delta opioid receptors and the sigma receptor was characterized. In the absence of sodium, the potency of opioid receptor competition at each receptor site was found to be: mu1-fentanyl > butorphanol > morphine > or = dezocine = nalbuphine; mu2-butorphanol > fentanyl > nalbuphine > morphine = dezocine; kappa1-butorphanol > nalbuphine >> morphine > or = dezocine > fentanyl; and delta-butorphanol > nalbuphine > or = dezocine > morphine > fentanyl. For all five compounds, competition at the sigma receptor was weak, with nalbuphine and dezocine having Kis of approximately 0.5 microM and the other opioids having Kis of greater than 1 microM. Since the presence of 100 mM NaCl during the competitive binding decreased the K(i), to varying degrees, of all five opioids at the mu1 and delta receptors and of some of the opioids at the mu2 and kappa1 receptors, the five compounds studied appear to differ in efficacy at the five receptor sites.
authors.affiliation: Department of Pharmacology, University of Massachusetts Medical Center, Worcester 01655.
authors.forename: J C
authors.initials: JC
authors.lastname: Chen
authors.forename: E R
authors.initials: ER
authors.lastname: Smith
authors.forename: M
authors.initials: M
authors.lastname: Cahill
authors.forename: R
authors.initials: R
authors.lastname: Cohen
authors.forename: J B
authors.initials: JB
authors.lastname: Fishman
mesh_terms: D000701:Analgesics, Opioid / Q000378:metabolism*; D000704:Analysis of Variance; D000818:Animals; D001667:Binding, Competitive; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002077:Butorphanol / Q000378:metabolism; D003516:Cycloparaffins / Q000378:metabolism; D005283:Fentanyl / Q000378:metabolism; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009020:Morphine / Q000378:metabolism; D009266:Nalbuphine / Q000378:metabolism; D009292:Narcotic Antagonists / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011957:Receptors, Opioid / Q000378:metabolism*; D013764:Tetrahydronaphthalenes
chemical_list: D000701:Analgesics, Opioid; D019086:Bridged Bicyclo Compounds, Heterocyclic; D003516:Cycloparaffins; D009292:Narcotic Antagonists; D011957:Receptors, Opioid; D013764:Tetrahydronaphthalenes; D009020:Morphine; D009266:Nalbuphine; D002077:Butorphanol; D005283:Fentanyl; C010827:dezocine