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Selective Modification of Short-Term Hippocampal Synaptic Plasticity and Impaired Memory Extinction in Mice with a Congenitally Reduced Hippocampal Commissure

UNCG Author/Contributor (non-UNCG co-authors, if there are any, appear on document)
Douglas Wahlsten, Visiting Professor (Creator)
Institution
The University of North Carolina at Greensboro (UNCG )
Web Site: http://library.uncg.edu/

Abstract: The hippocampus is critical for forming new long-term memories, but the contributions of the hippocampal commissure (HC) to memory function and hippocampal synaptic plasticity are unclear. To shed light on this issue, we characterized behavioral memory and hippocampal synaptic plasticity in two inbred mouse strains. BALB/cWah1 mice display a range of corpus callosal defects and an intact HC, whereas 9XCA/Wah mice exhibit a complete absence of corpus callosum and a greatly reduced HC. No differences between strains were found in long-term potentiation (LTP) within two synaptic pathways in hippocampal slices. However, paired-pulse facilitation was deficient in area CA1 of slices from 9XCA/Wah, and it was rescued by decreasing extracellular [Ca2+], suggesting that presynaptic calcium dynamics may be altered in this strain. In addition, contextual fear extinction was impaired in 9XCA/Wah mice, but performance on cued fear extinction and on 24 hr memory tests for cued and contextual fear conditioning were not significantly different between strains. Thus, an intact HC is critical for normal extinction of contextual fear. Intact interhemispheric connectivity is not required for acquisition or expression of cued and contextual fear conditioning. LTP was normal in slices from mice that lacked an intact HC, and this was correlated with normal performance on fear conditioning tests. In contrast, impaired short-term synaptic plasticity was correlated with defective contextual memory extinction in mice lacking an intact HC. Thus, the HC in mice is vital for particular aspects of memory function and for short-term synaptic modification in specific hippocampal circuits.

Additional Information

Publication
The Journal of Neuroscience, September 15, 2002, 22(18):8277–8286
Language: English
Date: 2002
Keywords
Hippocampal commissure, Memory, Learning , LTP, Fear conditioning, Extinction, Agenesis, Mouse strains, Synaptic plasticity