title: Post-acquisition hippocampal NMDA receptor blockade sustains retention of spatial reference memory in Morris water maze.
abstract: Several studies have demonstrated that the hippocampal N-methyl-D-aspartate type glutamate receptors (NMDARs) are necessary for the acquisition but not the retention of spatial reference memory. In contrast, a few studies have shown that post-acquisition repetitive intraperitoneal injections of an NMDAR antagonist facilitate the retention of spatial reference memory in a radial maze task. In the present study, we investigated the role of hippocampal NMDARs in the retention of spatial reference memories in Morris water maze. In Experiment 1, 24 h after training (4 trials/day for 4 days), D-AP5 was chronically infused into the hippocampus of rats for 5 days. In the subsequent probe test (seven days after training), we found that rats infused with D-AP5 spent a significantly longer time in the target quadrant compared to chance level, whereas rats in the control group did not. In Experiment 2, D-AP5 was infused into the hippocampus 1 (immediate) or 7 (delayed) days after the training session. In the probe test, following the retention interval of 13 days, immediate infusion facilitated the performance in a manner similar to Experiment 1, whereas the delayed infusion did not. These findings suggest that hippocampal NMDARs play an important role in the deterioration of spatial reference memory.
authors.affiliation: Faculty of Psychology, Doshisha University, Kyotanabe, Japan. Electronic address: ekn1004@mail2.doshisha.ac.jp.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Shinohara
authors.affiliation: Faculty of Psychology, Doshisha University, Kyotanabe, Japan.
authors.forename: Toshimichi
authors.initials: T
authors.lastname: Hata
mesh_terms: D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000818:Animals; D004305:Dose-Response Relationship, Drug; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D006624:Hippocampus / Q000378:metabolism*; D008297:Male; D018782:Maze Learning / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D012153:Retention, Psychology / Q000187:drug effects / Q000502:physiology*; D013028:Space Perception / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors
chemical_list: D018691:Excitatory Amino Acid Antagonists; D016194:Receptors, N-Methyl-D-Aspartate; D015763:2-Amino-5-phosphonovalerate
keywords: Forgetting; Hippocampus; NMDA receptor; Spatial reference memory