title: Physical separation of the agonist and antagonist forms of a mu opiate receptor?
abstract: The rabbit cerebellum contains up to 80% of mu opiate binding sites (J.C. Meunier, Life Sci. 31, 1327-1330 (1982) ). A crude membrane fraction derived therefrom was labelled either with the opiate agonist: 3H-etorphine or with the opiate antagonist: 3H-diprenorphine, and solubilized with digitonin. Centrifugation of the soluble extracts in linear sucrose gradients reveals that bound 3H-etorphine sediments faster than does bound 3H-diprenorphine: 12S vs 10S. The 3H-etorphine macromolecular complex (12S) is virtually absent in extracts of membranes that have been labelled in the presence of 120 mM NaCl or of 50 microM Gpp(NH)p (guanyl-5'-yl imidodiphosphate). Under the same conditions, recovery of 3H-diprenorphine in bound (10S) form is either not affected (Gpp(NH)p) or substantially increased (NaCl). These data are consistent with the notion that cerebellar mu opiate receptors may exist under physically separable agonist and antagonist states.
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002531:Cerebellum / Q000378:metabolism*; D004174:Diprenorphine / Q000378:metabolism*; D005048:Etorphine / Q000378:metabolism*; D009019:Morphinans / Q000378:metabolism*; D011817:Rabbits; D011957:Receptors, Opioid / Q000302:isolation & purification / Q000378:metabolism*; D017450:Receptors, Opioid, mu; D012995:Solubility
chemical_list: D009019:Morphinans; D011957:Receptors, Opioid; D017450:Receptors, Opioid, mu; D004174:Diprenorphine; D005048:Etorphine