Hippocampal NMDA receptors are involved in rats׳ spontaneous object recognition only under high memory load condition

Hippocampal NMDA receptors are involved in rats׳ spontaneous object recognition only under high... The possible involvement of hippocampal N-methyl-d-aspartate (NMDA) receptors in spontaneous object recognition was investigated in rats under different memory load conditions. We first estimated rats׳ object memory span using 3–5 objects in “Different Objects Task (DOT)” in order to confirm the highest memory load condition in object recognition memory. Rats were allowed to explore a field in which 3 (3-DOT), 4 (4-DOT), or 5 (5-DOT) different objects were presented. After a delay period, they were placed again in the same field in which one of the sample objects was replaced by another object, and their object exploration behavior was analyzed. Rats could differentiate the novel object from the familiar ones in 3-DOT and 4-DOT but not in 5-DOT, suggesting that rats׳ object memory span was about 4. Then, we examined the effects of hippocampal AP5 infusion on performance in both 2-DOT (2 different objects were used) and 4-DOT. The drug treatment before the sample phase impaired performance only in 4-DOT. These results suggest that hippocampal NMDA receptors play a critical role in spontaneous object recognition only when the memory load is high. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Brain Research Elsevier

Hippocampal NMDA receptors are involved in rats׳ spontaneous object recognition only under high memory load condition

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Publisher
Elsevier
Copyright
Copyright © 2015 Elsevier B.V.
ISSN
0006-8993
D.O.I.
10.1016/j.brainres.2015.08.001
Publisher site
See Article on Publisher Site

Abstract

The possible involvement of hippocampal N-methyl-d-aspartate (NMDA) receptors in spontaneous object recognition was investigated in rats under different memory load conditions. We first estimated rats׳ object memory span using 3–5 objects in “Different Objects Task (DOT)” in order to confirm the highest memory load condition in object recognition memory. Rats were allowed to explore a field in which 3 (3-DOT), 4 (4-DOT), or 5 (5-DOT) different objects were presented. After a delay period, they were placed again in the same field in which one of the sample objects was replaced by another object, and their object exploration behavior was analyzed. Rats could differentiate the novel object from the familiar ones in 3-DOT and 4-DOT but not in 5-DOT, suggesting that rats׳ object memory span was about 4. Then, we examined the effects of hippocampal AP5 infusion on performance in both 2-DOT (2 different objects were used) and 4-DOT. The drug treatment before the sample phase impaired performance only in 4-DOT. These results suggest that hippocampal NMDA receptors play a critical role in spontaneous object recognition only when the memory load is high.

Journal

Brain ResearchElsevier

Published: Oct 22, 2015

References

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