title: Modulation of muscimol state-dependent memory by α2-adrenoceptors of the dorsal hippocampal area.
abstract: In the present study, the effects of bilateral intra-dorsal hippocampal (intra-CA1) injections of α2-adrenoceptor agonist and antagonist, on muscimol state-dependent memory were examined in mice. A single-trial step-down passive avoidance task was used for the assessment of memory retention in adult male NMRI mice. Administration of muscimol (0.1 μg/mouse, intra-CA1) 15 min before training or testing induced impairment of memory retention. Injection of the same dose of the drug 15 min before testing restored memory retention impaired under pre-training muscimol influence. Pre-test intra-CA1 administration of the α2-adrenoceptor agonist clonidine (0.5 and 1 μg/mouse) impaired memory retention, although the low dose of the drug (0.25 μg/mouse) did not affect memory retention. Pre-test intra-CA1 administration of the α2-adrenoceptor antagonist yohimbine (1 and 2 μg/mouse) improved memory retention, although the low dose of the drug (0.5 μg/mouse) did not affect memory retention. In other series of experiments, pre-test co-administration of certain doses of clonidine (0.125 and 0.25 μg/mouse, intra-CA1), doses which were ineffective when given alone, and muscimol (0.1 μg/mouse, intra-CA1) significantly inhibited muscimol state-dependent memory. Pre-test intra-CA1 administration of certain doses of yohimbine (0.25 and 0.5 μg/mouse), doses which were ineffective when given alone, improved pre-training muscimol (0.1 μg/mouse)-induced retrieval impairment. Moreover, pre-test co-administration of yohimbine (0.25 and 0.5 μg/mouse, intra-CA1) and muscimol (0.025 μg/mouse, intra-CA1), an ineffective dose, significantly restored the retrieval and induced muscimol state-dependent memory. It may be concluded that the α2-adrenoceptors of 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. jafarisa@sina.tums.ac.ir
authors.forename: Majid
authors.initials: M
authors.lastname: Jafari-Sabet
authors.forename: Hamid R
authors.initials: HR
authors.lastname: Banafshe
authors.forename: Mohammad-Amin
authors.initials: MA
authors.lastname: Khodadadnejad
mesh_terms: D058647:Adrenergic alpha-2 Receptor Agonists / Q000494:pharmacology; D058669:Adrenergic alpha-2 Receptor Antagonists; D000818:Animals; D001362:Avoidance Learning; D056547:CA1 Region, Hippocampal / Q000502:physiology*; D003000:Clonidine / Q000494:pharmacology; D058785:GABA-A Receptor Agonists / Q000008:administration & dosage*; D008297:Male; D008569:Memory Disorders / Q000503:physiopathology*; D051379:Mice; D009118:Muscimol / Q000008:administration & dosage*; D018341:Receptors, Adrenergic, alpha-2 / Q000502:physiology*; D015016:Yohimbine / Q000494:pharmacology
chemical_list: D058647:Adrenergic alpha-2 Receptor Agonists; D058669:Adrenergic alpha-2 Receptor Antagonists; D058785:GABA-A Receptor Agonists; D018341:Receptors, Adrenergic, alpha-2; D009118:Muscimol; D015016:Yohimbine; D003000:Clonidine