behavior/neurological
• while mutants show similar freezing response to footshocks during training, they show less freezing time in the absence of footshocks when reintroduced to the same cage 24 hours later, suggesting suppressed fear memory consolidation
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• mice show decreased numbers of spontaneous alternations in the Y maze, indicating impaired spatial recognition memory
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nervous system
• dentate gyrus granule neurons show decreased AMPA receptor surface levels
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• dendritic spine density in the molecular layer is reduced
• decrease in spine width and increase in spine length of dentate gyrus granule neuron dendrites
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• decrease in spine width and increase in spine length of dentate gyrus granule neuron dendrites
• however, hippocampal organization, number of granule neurons in the dentate gyrus, and dendrite length and complexity of dentate gyrus granule cells are normal
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• prepulse inhibition is substantially lower in mutants indicating impaired sensorimotor gating
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• dentate gyrus granule neurons show impaired excitatory synaptic activity and compromised glutamatergic transmission
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• postsynaptic current (sEPSC) charge transfer, but normal spontaneous inhibitory postsynaptic current (sIPSC) charge transfer, resulting in an almost 50% decrease in sEPSC/sIPSC ratio
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• amplitudes of evoked EPSCs, but not evoked IPSCs, are reduced when the medial performant pathway is stimulated at gradual increasing intensity
• however, paired-pulse ratios of evoked EPSC in dentate gyrus granule neurons are similar to wild-type neurons, indicating little effect on glutamate release
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• however, miniature IPSCs are normal
• the frequency and amplitude of miniature EPSCs in dentate gyrus neurons are decreased
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• prepulse inhibition is substantially lower in mutants
• however, baseline startle responses are normal, indicating normal hearing and acoustic startle reflex
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