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Experience-specific plasticity at excitatory and inhibitory synapses onto granule cells in the dentate gyrus

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Title
海馬歯状回の顆粒細胞における経験特異的なシナプス可塑性
Experience-specific plasticity at excitatory and inhibitory synapses onto granule cells in the dentate gyrus
Degree 博士(医学) Dissertation Number 医博甲第1629号 (2022-03-16)
Degree Grantors Yamaguchi University
[kakenhi]15501 grid.268397.1
Abstract
The hippocampal dentate gyrus has been identified to play a critical role in maintaining contextual memory in many mammalian species. To evaluate learning-induced synaptic plasticity of granule cells, we subjected male rats to an inhibitory avoidance (IA) task and prepared acute hippocampal slices. In the presence of 0.5 µM tetrodotoxin, we recorded miniature EPSCs in male rats experiencing four groups: untrained, IA-trained, unpaired, and walk-through. Compared with the untrained, IA-trained, unpaired, and walk-through groups, the unpaired group significantly enhanced mean mEPSC amplitudes, suggesting the experience-induced plasticity at AMPA receptor-mediated excitatory synapses. For inhibitory synapses, both unpaired and walk-through groups significantly decreased mean mIPSC amplitudes, showing the experience-induced reduction of postsynaptic GABA_A receptor-mediated currents. Unlike the plasticity at CA1 synapses, it was difficult to explain the learning-specific plasticity at the synapses. However, overall multivariate analysis using four variables of mE(I)PSC responses revealed experience-specific changes in the diversity, suggesting that the diversity of excitatory/inhibitory synapses onto granule cells differs among the past experience of animals include the learning.
In comparison with CA1 pyramidal neurons, granule cells consistently showed greater amplitude and frequency of mE(I)PSCs. Fluctuation analysis further revealed that granule cells provide more postsynaptic AMPA receptor channels and greater single-channel current of GABA_A receptors of than CA1 pyramidal neurons. These findings show functional differences between two types of principal cells in the hippocampus.
Creators Han Thiri Zin
Creator Keywords
AMPA receptor GABA_A receptor GABA glutamic acid contextual learning synaptic plasticity granule cells
Languages eng
Resource Type doctoral thesis
File Version Version of Record
Access Rights open access
Schools 大学院医学系研究科(医学)