title: Nitric oxide in the dorsal hippocampal area is involved on muscimol state-dependent memory in the step-down passive avoidance test.
abstract: In the present study, the effects of intra-dorsal hippocampal (intra-CA1) injections of nitric oxide (NO) agents on muscimol state-dependent memory were examined in mice. A single-trial step-down passive avoidance task was used for the assessment of memory retrieval in adult male NMRI mice. Post-training intra-CA1 administration of a GABAA receptor agonist, muscimol (0.05 and 0.1 μg/mouse) dose dependently induced impairment of memory retention. Pre-test injection of muscimol (0.05 and 0.1 μg/mouse) induced state-dependent retrieval of the memory acquired under post-training muscimol (0.1 μg/mouse, intra-CA1) influence. Pre-test injection of a NO precursor, L-arginine (1 and 2 μg/mouse, intra-CA1) improved memory retention, although the low dose of the drug (0.5 μg/mouse) did not affect memory retention. Pre-test injection of an inhibitor of NO-synthase, L-NAME (0.5 and 1 μg/mouse, intra-CA1) impaired memory retention, although the low dose of the drug (0.25 μg/mouse) did not affect memory retention. In other series of experiments, pre-test intra-CA1 injection of L-arginine (0.25 and 0.5 μg/mouse) 5 min before the administration of muscimol (0.1 μg/mouse, intra-CA1) dose dependently inhibited muscimol state-dependent memory. Pre-test intra-CA1 administration of L-arginine (0.125, 0.25 and 0.5 μg/mouse) by itself cannot affect memory retention. Pre-test intra-CA1 injection of L-NAME (0.25 μg/mouse, intra-CA1) reversed the memory impairment induced by post-training administration of muscimol (0.1 μg/mouse, intra-CA1). Moreover, pre-test administration of L-NAME (0.125 and 0.25 μg/mouse, intra-CA1) with an ineffective dose of muscimol (0.025 μg/mouse, intra-CA1) significantly restored the retrieval and induced muscimol state-dependent memory. Pre-test intra-CA1 administration of L-NAME (0.0625, 0.125 and 0.25 μg/mouse) by itself cannot affect memory retention. It may be suggested that the nitric oxide in the dorsal hippocampal area play an important role in muscimol state-dependent memory.
authors.affiliation: Department of Pharmacology, School of Medicine, AJA University of Medical Sciences, Tehran, Iran. Electronic address: jafarisa@sina.tums.ac.ir.
authors.forename: Majid
authors.initials: M
authors.lastname: Jafari-Sabet
authors.affiliation: Department of Pharmacology, School of Medicine, AJA University of Medical Sciences, Tehran, Iran.
authors.forename: Mohammad-Amin
authors.initials: MA
authors.lastname: Khodadadnejad
authors.affiliation: Department of Pharmacology, School of Medicine, AJA University of Medical Sciences, Tehran, Iran.
authors.forename: Saeed
authors.initials: S
authors.lastname: Ghoraba
authors.affiliation: Department of Toxicology and Pharmacology, Faculty of Pharmacy, Mazandaran University of Medical Sciences, Sari, Iran.
authors.forename: Ramin
authors.initials: R
authors.lastname: Ataee
mesh_terms: D000818:Animals; D001120:Arginine / Q000008:administration & dosage; D001362:Avoidance Learning; D056547:CA1 Region, Hippocampal / Q000502:physiology*; D008297:Male; D008568:Memory; D051379:Mice; D009118:Muscimol / Q000008:administration & dosage*; D019331:NG-Nitroarginine Methyl Ester / Q000008:administration & dosage; D009569:Nitric Oxide / Q000502:physiology*
chemical_list: D009118:Muscimol; D009569:Nitric Oxide; D001120:Arginine; D019331:NG-Nitroarginine Methyl Ester
keywords: Dorsal hippocampus; Mice; Muscimol; State-dependent memory; l-NAME; l-arginine