Cerebral Cortex Advance Access originally published online on February 9, 2005
Cerebral Cortex 2005 15(11):1703-1713; doi:10.1093/cercor/bhi047
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The Metabotropic Glutamate Receptor, mGluR5, is a Key Determinant of Good and Bad Spatial Learning Performance and Hippocampal Synaptic Plasticity
1 Learning and Memory Research, International Graduate School for Neuroscience, Ruhr University Bochum, FNO 1/116, Universitaetsstrasse 150, 44780 Bochum, Germany, 2 Institute of Physiology of the Charite, Synaptic Plasticity Research Group, Humboldt University, Tucholskystrasse 2, 10117 Berlin, Germany and 3 Neuroscience Research Center of the Charite, Signal Transduction Research Group, Humboldt University, Tucholskystrasse 2, 10117 Berlin, Germany
Address correspondence to Denise Manahan-Vaughan, International Graduate School of Neuroscience, Learninf and Memory Research, Ruhr-Universität Bochum, FNO 01/116, Universitaetstr. 150, 44780 Bochum, Germany. E-mail: dmv{at}neurobiologie.rub.de, vaughan{at}neurobiologie.rub.de.
Hippocampal synaptic plasticity is expressed to very different extents in distinct rat strains in vivo. This may correlate with differences in learning ability. We investigated whether the metabotropic glutamate receptor mGluR5 contributes to differences in long-term potentiation (LTP) and learning in freely moving hooded Lister (HL) and Wistar rats. High-frequency tetanization (HFT) generated robust CA1 LTP in Wistar rats (> 24 h) and incremental potentiation in HL rats. The mGluR5 antagonist 2-methyl-6-(phenylethynyl) pyridine (MPEP; 1.8 µg), applied intracerebrally, impaired LTP from 
60 min onwards in Wistar and from 24 h in HL rats. HFT generated LTP in the dentate gyrus (DG) of Wistar rats (> 24 h), which was blocked by MPEP, and MPEP-resistant short-term depression in HL rats. Training for 10 days in an eight-arm radial maze revealed no working memory differences, but better reference memory performance in Wistar compared with HL rats. Daily application of MPEP (1.8 µg) impaired working and reference memory in Wistar rats. In HL rats, working memory was impaired but reference memory was unaffected. Western blot analysis revealed lower expression of mGluR5 in HL compared with Wistar rats. MGluR1 expression was equivalent. These data reveal striking mGluR5-dependent differences in spatial learning in different rat strains, which correlate to synaptic plasticity and mGluR5 expression levels.
Key Words: CA1 • dentate gyrus • hooded Lister • long-term potentiation • MPEP • Wister
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