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Synaptic Plasticity

開催日 2014/9/11
時間 16:00 - 17:00
会場 Poster / Exhibition(Event Hall B)

Control of intrinsic excitability of layer 3/4 neurons in primary auditory cortex of blind mice

  • P1-060
  • 鈴木 俊雄 / Toshio Suzuki:1 川井 D 秀樹 / Hideki Dere Kawai:1 
  • 1:創価大学大学院 工学研究科 生命情報工学専攻 / Dept Bioinformatics, Graduate School of Engineering, Soka University,Tokyo, Japan 

Cross-modal plasticity leads to changes in cortical function following sensory deprivation in another modality. It was recently reported, for example, that thalamocortical inputs are potentiated in the thalamo-recipient layers (layers 3/4) of primary auditory cortex (A1) in mice visually deprived early in life. Their cellular and synaptic mechanisms as well as other changes that could occur remain to be understood. Here, we investigated if and how changes in neuronal membrane properties occur in layers 3/4 neurons in A1 of blind mice. In particular, we examined the regulation of neuronal excitability by acetylcholine (ACh) and by a repetitive high-frequency firing.
To use early blind mice, we operated for binocular deprivation (enucleation) on mice at the time of eye opening (postnatal days 14-15). After rearing for 8-12 days, we prepared auditory thalamocortical slices in blind and sighted control mice and examined neuronal membrane properties in layer 3/4 neurons using the whole-cell patch-clamp recording technique.
Effects of enucleation on intrinsic properties were not apparent between control and blind mice. However, sensitivity to stimulation of muscarinic acetylcholine receptors by ACh (<100 μM in the bath) differed. Thus, ACh greatly increased resting membrane potentials (RMPs) in the control, but less so in the blind. The magnitude of the changes in RMPs was about two-fold less in the blind, suggesting that cholinergic control of neuronal excitability is compromised.
Meanwhile, a brief period of induced-repetitive high-frequency firing (15 times at 40 Hz for 10 min at 0.25 Hz) altered neuronal excitability differently. The repetitive firing depressed RMPs rapidly within 30 sec during stimulation, which further declined gradually in the control, but remained nearly the same level in the blind mice. After the stimulation, RMPs returned to the baseline level in the control, but they were elevated more than the baseline in the blind for at least the duration of the recordings (~25 min). These data suggest that regulatory mechanisms of intrinsic excitability in layer 3/4 neurons have been altered by cross-modal plasticity.

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