title: Nociceptin receptors in the rat spinal cord during morphine tolerance.
abstract: The anatomical localization of nociceptin receptors was examined by in vitro quantitative autoradiography techniques in rat spinal cord sections by using [(125)I-Tyr(14)]nociceptin. [(125)I-Tyr(14)]nociceptin appeared to interact with a single class of binding sites (K(D)=0.1 nM) present in the grey matter in all laminae of the spinal cord from cervical to sacral levels. Pre-incubation of sections in the presence of 150 mM NaCl, did not modify the radioligand affinity but significantly augmented the number of accessible binding sites and increased specific binding of [(125)I-Tyr(14)]nociceptin differentially on each laminae. In particular, the superficial layers of the dorsal horn exhibited the highest density of sites after pre-wash. Continuous intrathecal infusion of morphine produced a tolerance accompanied by a significant increase in nociceptin site density in the superficial layers. Thus, nociceptin binding sites may have different properties dependent upon the layer and may be up-regulated during the process of opioid-induced tolerance.
authors.affiliation: Institut de Pharmacologie et de Biologie Structurale, CNRS, 205 Route de Narbonne, 31077, Toulouse, France.
authors.forename: C
authors.initials: C
authors.lastname: Gouardères
authors.forename: J A
authors.initials: JA
authors.lastname: Tafani
authors.forename: J C
authors.initials: JC
authors.lastname: Meunier
authors.forename: K
authors.initials: K
authors.lastname: Jhamandas
authors.forename: J M
authors.initials: JM
authors.lastname: Zajac
mesh_terms: D000595:Amino Acid Sequence; D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D001345:Autoradiography; D004361:Drug Tolerance; D007457:Iodine Radioisotopes; D008297:Male; D008969:Molecular Sequence Data; D009020:Morphine / Q000494:pharmacology*; D011869:Radioligand Assay; D051381:Rats; D017207:Rats, Sprague-Dawley; D011957:Receptors, Opioid / Q000032:analysis / Q000187:drug effects*; D013116:Spinal Cord / Q000737:chemistry / Q000187:drug effects*; D000094942:Nociceptin Receptor
chemical_list: D000701:Analgesics, Opioid; D007457:Iodine Radioisotopes; D009020:Morphine; D011957:Receptors, Opioid; D000094942:Nociceptin Receptor; C000722285:Oprl1 protein, rat