Dissociation of the roles of NMDA receptor and hippocampus in rats' spatial learning: the effects of environmental familiarity and task familiarity.
In this study, we compared the effects of MK-801 and hippocampal lesions on re-training of Morris water maze place task in familiar and novel environments in rats. In Experiment 1, rats were pre-trained with the place task. After acquiring the task, rats were re-trained with the same task in a familiar environment following MK-801 injection, and were then trained with the same task in a novel environment following MK-801 injection. In the familiar environment, MK-801 had no effect, but in the novel environment performance was impaired. In Experiment 2, after the place task training, the hippocampus was lesioned, and rats were re-trained with the same task in the familiar environment then retrained again in the novel environment. Rats showed severe impairment in both environments. These two experiments suggest different functions for NMDA receptors and the hippocampus. The results of Experiment 1 showed that NMDA receptors are not required for utilizing spatial representations but they play an important role in the construction of spatial representations. The results of Experiment 2 show that the hippocampus is necessary for both the utilization of spatial representations already formed and the formation of new spatial representations.
Uekita
Tomoko
T
Department of Psychology, Faculty of Letters, Doshisha University, Japan. ela3502@mail2.doshisha.ac.jp
Okaichi
Yoko
Y
Okaichi
Hiroshige
H
D000818:Animals; D003714:Denervation; D004195:Disease Models, Animal; D004780:Environment, Controlled; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000378:metabolism; D006624:Hippocampus / Q000187:drug effects / Q000293:injuries / Q000503:physiopathology*; D007858:Learning / Q000187:drug effects / Q000502:physiology*; D007859:Learning Disabilities / Q000139:chemically induced / Q000503:physiopathology; D008297:Male; D018782:Maze Learning / Q000187:drug effects / Q000502:physiology; D008569:Memory Disorders / Q000139:chemically induced / Q000503:physiopathology*; D009949:Orientation / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013028:Space Perception / Q000187:drug effects / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology
D018691:Excitatory Amino Acid Antagonists; D016194:Receptors, N-Methyl-D-Aspartate; D018698:Glutamic Acid