title: Effects of glycogen synthase kinase 3beta and cyclin-dependent kinase 5 inhibitors on morphine-induced analgesia and tolerance in rats.
abstract: Repeated administration of morphine is associated with the development of tolerance, yet the mechanism underlying this phenomenon is still poorly understood. Recent evidence implicating glycogen synthase kinase 3 (GSK3) in opioid receptor signaling pathways has prompted us to investigate its role in morphine tolerance. Administration of 10 mg/kg morphine i.p. to Wistar rats twice daily for 8 days resulted in complete tolerance to its analgesic effects as measured by the tail-flick test. When injections of morphine were preceded by intrathecal (i.t.) administration of either an inhibitor of GSK3 [(3-(2,4-dichlorophenyl)-4-(1-methyl-1H-indol-3-yl)-1H-pyrrole-2,5-dione (SB216763) or 6-bromoindirubin-3'oxime] or an inhibitor of cyclin-dependent kinase (Cdk), roscovitine, development of tolerance to morphine analgesia was completely abolished. In addition, a single i.t. injection of either kinase inhibitor was able to restore in a dose-dependent manner the analgesic effect of morphine in morphine-tolerant rats. None of the inhibitors in doses used in the present study had analgesic effects of their own nor an effect on the analgesic potency of morphine. Repeated i.t. administration of either inhibitor had caused an increase in abundance of GSK-3beta phosphorylated at Ser(9) in the dorsal lumbar part of the spinal cord of rats that were chronically treated with morphine. Furthermore, reversal of morphine tolerance by a single injection of either inhibitor was always associated with increased abundance of phospho-GSK3beta. In conclusion, our data indicate that chronic morphine treatment activates a highly efficient pathway by means of which Cdk5 regulates GSK3beta activity.
authors.affiliation: Department of Molecular Neuropharmacology, Institute of Pharmacology PAS, 12 Smetna St., 31-343 Krakow, Poland.
authors.forename: Jan Rodriguez
authors.initials: JR
authors.lastname: Parkitna
authors.forename: Ilona
authors.initials: I
authors.lastname: Obara
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Wawrzczak-Bargiela
authors.forename: Wioletta
authors.initials: W
authors.lastname: Makuch
authors.forename: Barbara
authors.initials: B
authors.lastname: Przewlocka
authors.forename: Ryszard
authors.initials: R
authors.lastname: Przewlocki
mesh_terms: D000698:Analgesia; D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D051360:Cyclin-Dependent Kinase 5 / Q000037:antagonists & inhibitors / Q000502:physiology*; D051937:Dopamine and cAMP-Regulated Phosphoprotein 32 / Q000378:metabolism; D004361:Drug Tolerance; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors / Q000502:physiology*; D000071679:Glycogen Synthase Kinase 3 beta; D007211:Indoles / Q000494:pharmacology; D008297:Male; D008301:Maleimides / Q000494:pharmacology; D009020:Morphine / Q000494:pharmacology*; D017288:Pain Threshold / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D013116:Spinal Cord / Q000187:drug effects / Q000378:metabolism
chemical_list: D000701:Analgesics, Opioid; D051937:Dopamine and cAMP-Regulated Phosphoprotein 32; D007211:Indoles; D008301:Maleimides; C497930:Ppp1r1b protein, rat; C417521:SB 216763; D009020:Morphine; D051360:Cyclin-Dependent Kinase 5; D000071679:Glycogen Synthase Kinase 3 beta; C000605508:Gsk3b protein, rat; C495907:Cdk5 protein, rat; D038362:Glycogen Synthase Kinase 3