title: Involvement of dorsal hippocampal muscarinic cholinergic receptors on muscimol state-dependent memory of passive avoidance in mice.
abstract: OBJECTIVE
  In the present study, the effects of bilateral intra-dorsal hippocampal (intra-CA1) injections of cholinergic agents on muscimol state-dependent memory were examined in mice.
  
  
  METHODS
  A single-trial step-down passive avoidance task was used for the assessment of memory retention in adult male NMRI mice.
  
  
  RESULTS
  Pre-training intra-CA1 administration of a GABA-A 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, intra-CA1) induced state-dependent retrieval of the memory acquired under pre-training muscimol (0.1 μg/mouse, intra-CA1) influence. Pre-test intra-CA1 injection of an acetylcholinesterase inhibitor, physostigmine (0.5 and 1 μg/mouse, intra-CA1) reversed the memory impairment induced by pre-training administration of muscimol (0.1 μg/mouse, intra-CA1). Moreover, pre-test administration of physostigmine (0.5 and 1 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 physostigmine (0.25, 0.5 and 1 μg/mouse) by itself cannot affect memory retention. Pre-test intra-CA1 injection of the muscarinic receptor antagonist, atropine (1 and 2 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 atropine (0.5, 1 and 2 μg/mouse) by itself cannot affect memory retention.
  
  
  CONCLUSIONS
  The results suggest that muscarinic cholinergic mechanism of the CA1 may influence 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
mesh_terms: D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001362:Avoidance Learning / Q000187:drug effects*; D001522:Behavior, Animal / Q000187:drug effects; D056547:CA1 Region, Hippocampal / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D002800:Cholinesterase Inhibitors / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D058785:GABA-A Receptor Agonists / Q000494:pharmacology*; D008297:Male; D008568:Memory / Q000187:drug effects*; D051379:Mice; D008815:Mice, Inbred Strains; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009118:Muscimol / Q000494:pharmacology*; D011976:Receptors, Muscarinic / Q000378:metabolism*
chemical_list: D002800:Cholinesterase Inhibitors; D058785:GABA-A Receptor Agonists; D018727:Muscarinic Antagonists; D011976:Receptors, Muscarinic; D009118:Muscimol; D001285:Atropine