title: Role of dorsal hippocampal orexin-1 receptors in memory restoration induced by morphine sensitization phenomenon.
abstract: The present study was examined the blockade of CA1 orexin-1 receptors (OX1Rs) of the dorsal hippocampus in the induction or expression phase on morphine sensitization-induced memory restoration using the Morris water maze (MWM) apparatus. Results showed that pre-training administration of morphine (5mg/kg, s.c.) increases escape latency and traveled distance, while does not alter swimming speed. This supports the impairing effect of morphine on the spatial memory acquisition in male adult rats. Also, in the retrieval session (probe trial) this treatment decreased the time spent in the target quadrant. Moreover, morphine-induced sensitization (15 or 20mg/kg, s.c.; once daily for 3days and followed by 5days no drug treatment) restored the memory acquisition/retrieval deficit which had been induced by pre-training administration of morphine (5mg/kg, s.c.). Intra-CA1 microinjection of subthreshold doses of SB-334867 (OX1Rs antagonist; 10, 20 and 40nmol/rat), 5min before morphine (20mg/kg/day×3days, s.c.; induction phase for morphine sensitization) did not alter restoration of memory acquisition/retrieval produced by the morphine sensitization phenomenon. In contrast, microinjection of subthreshold doses of SB-334867 (10, 20 and 40nmol/rat) into the CA1 region in the training session, 5min prior to morphine (5mg/kg, s.c.; expression phase for morphine sensitization) blocked the spatial memory acquisition/retrieval in morphine-sensitized rats. In conclusion, these findings show that morphine sensitization reverses morphine-induced amnesia. Furthermore, the blockade of CA1 OX1Rs in the expression phase, but not in the induction phase, disrupts memory restoration induced by morphine sensitization.
authors.affiliation: Department of Biology, Faculty of Science, Gonbad Kavous University, Gonbad Kavous, Iran.
authors.forename: S
authors.initials: S
authors.lastname: Alijanpour
authors.affiliation: Department of Neuroscience, School of Advanced Technologies in Medicine, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: F
authors.initials: F
authors.lastname: Tirgar
authors.affiliation: Institute for Cognitive Science Studies (ICSS), Tehran, Iran; Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran; Iranian National Center for Addiction Studies, Tehran University of Medical Sciences, Tehran, Iran; School of Cognitive Sciences, Institute for Research in Fundamental Sciences (IPM), Tehran, Iran. Electronic address: zarinmr@ams.ac.ir.
authors.forename: M-R
authors.initials: MR
authors.lastname: Zarrindast
mesh_terms: D000647:Amnesia / Q000139:chemically induced* / Q000188:drug therapy; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D001583:Benzoxazoles / Q000008:administration & dosage / Q000494:pharmacology; D056547:CA1 Region, Hippocampal / Q000187:drug effects*; D059333:Central Nervous System Sensitization / Q000187:drug effects / Q000502:physiology*; D008297:Male; D018782:Maze Learning / Q000187:drug effects / Q000502:physiology; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology*; D009287:Naphthyridines; D009294:Narcotics / Q000008:administration & dosage / Q000494:pharmacology*; D064446:Orexin Receptors / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D018013:Receptors, Neuropeptide / Q000037:antagonists & inhibitors; D065852:Spatial Memory / Q000187:drug effects* / Q000502:physiology; D014508:Urea / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: C420062:1-(2-methylbenzoxazol-6-yl)-3-(1,5)naphthyridin-4-yl urea; D001583:Benzoxazoles; C578627:Hcrtr1 protein, rat; D009287:Naphthyridines; D009294:Narcotics; D064446:Orexin Receptors; D018013:Receptors, Neuropeptide; D009020:Morphine; D014508:Urea
keywords: CA1 regions; OX(1) receptors; morphine sensitization; morris water maze; rat