title: Anesthetic ketamine impairs rats' recall of previous information: the nitric oxide synthase inhibitor N-nitro-L-arginine methylester antagonizes this ketamine-induced recognition memory deficit.
abstract: BACKGROUND
  There is poor experimental evidence concerning the effects of anesthetic doses of the noncompetitive N-methyl-D-aspartate receptor antagonist ketamine on rodents' memory abilities. The current study was designed (1) to investigate the consequences of posttraining administration of anesthetic ketamine (100 mg/kg intraperitoneally) on rats' recognition memory and (2) to evaluate the ability of the nitric oxide synthase inhibitor N-nitro-L-arginine methylester (L-NAME; 1, 3, and 10 mg/kg intraperitoneally) to counteract the expected behavioral deficits produced by anesthetic ketamine. Finally, in an attempt to clarify if the expected memory impairments produced by anesthetic ketamine were related to the anesthesia, we also tested the effects of a subanesthetic dose of it (3 mg/kg intraperitoneally) on rats' recognition memory.
  
  
  METHODS
  The novel object recognition test, a procedure assessing recognition memory in rats, was selected.
  
  
  RESULTS
  Posttraining administration of anesthetic (but not of subanesthetic) ketamine disrupted rats' performance in the novel object recognition paradigm. The discrimination index (D) was decreased by ketamine from 0.415 (using saline) to 0.128, thus indicating that the anesthetic dose of ketamine impaired recognition memory. L-NAME (1-3, but not 10, mg/kg) reversed this memory deficit produced by ketamine; the D index of 0.128 using ketamine treatment was increased by 1 and 3 mg/kg L-NAME to 0.427 and 0.478, respectively.
  
  
  CONCLUSIONS
  The current results indicate that anesthetic ketamine impaired rats' posttraining memory components (storage and/or retrieval of information) and that a nitric oxide component modulates its behavioral effects.
authors.affiliation: Department of Pharmacology, School of Medicine, University of Thessaly, Larissa, Greece.
authors.forename: Antonios
authors.initials: A
authors.lastname: Boultadakis
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Pitsikas
mesh_terms: D000778:Anesthetics, Dissociative / Q000037:antagonists & inhibitors / Q000633:toxicity; D000818:Animals; D004791:Enzyme Inhibitors / Q000494:pharmacology / Q000627:therapeutic use; D007649:Ketamine / Q000037:antagonists & inhibitors / Q000633:toxicity*; D008297:Male; D008569:Memory Disorders / Q000139:chemically induced* / Q000201:enzymology / Q000517:prevention & control; D011939:Mental Recall / Q000187:drug effects* / Q000502:physiology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology* / Q000627:therapeutic use; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011446:Prospective Studies; D051381:Rats; D017208:Rats, Wistar; D021641:Recognition, Psychology / Q000187:drug effects* / Q000502:physiology
chemical_list: D000778:Anesthetics, Dissociative; D004791:Enzyme Inhibitors; D007649:Ketamine; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester