title: Post-training N-methyl-D-aspartate receptor blockade offers protection from retrograde interference but does not affect consolidation of weak or strong memory traces in the water maze.
abstract: Memory consolidation is the process where labile memory traces become long-lasting, stable memories. Previous work has demonstrated that spatial memory consolidation, several days after training in a water maze had ceased, can be disrupted by a temporary intra hippocampal infusion of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/kainate antagonist LY326325 (Riedel et al., 1999). Such reversible pharmacological techniques offer advantages over the permanent lesion studies that had first suggested a role for the hippocampus in memory consolidation. However, to date the role of N-methyl-D-aspartate receptors in such systems level processes remains controversial with evidence for impairments and augmentation of performance. Here we investigate the role of post-training hippocampal N-methyl-D-aspartate receptor blockade in rats and mice on the consolidation of weak and strong memory traces using an Atlantis water maze protocol. A hidden Atlantis platform was employed and rats (experiments 1 and 2) and mice (experiment 3) were required to dwell within 20 cm of the trained location to activate and subsequently reveal the escape platform. In experiments 1 and 3 a strong memory trace was established by training rats or mice for several days in the water maze. In experiment 2 a significantly weaker trace was instituted by reducing the training period. N-methyl-D-aspartate receptor blockade was induced after the last training trial and continued for seven days. Reliable memory for the trained platform location in a retention test 15 days after the last training day demonstrated that N-methyl-D-aspartate receptor blockade did not affect memory consolidation in rats or mice. Our results also show that post-training N-methyl-D-aspartate receptor blockade can lead to better performance in further retention tests conducted after the consolidation and drug administration period. Those data suggest that specific post-training N-methyl-D-aspartate receptor blockade does not impair memory consolidation and it may also offer a memory trace mild protection from retrograde interference.
authors.affiliation: Laboratory for Cognitive Neuroscience, Centre for Neuroscience Research, University of Edinburgh, 1 George Square, Edinburgh EH8 9JZ, Scotland, UK. Daym1@wyeth.com
authors.forename: M
authors.initials: M
authors.lastname: Day
authors.forename: R F
authors.initials: RF
authors.lastname: Langston
mesh_terms: D000818:Animals; D004594:Electrophysiology; D018691:Excitatory Amino Acid Antagonists / Q000008:administration & dosage; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D007276:Injections, Intraventricular; D008297:Male; D018782:Maze Learning / Q000187:drug effects / Q000502:physiology*; D008568:Memory / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors*; D012153:Retention, Psychology / Q000187:drug effects / Q000502:physiology*
chemical_list: D018691:Excitatory Amino Acid Antagonists; D016194:Receptors, N-Methyl-D-Aspartate