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Synaptic Plasticity

開催日 2014/9/12
時間 14:00 - 15:00
会場 Poster / Exhibition(Event Hall B)

Regulation of backpropagating action potential along hippocampal CA1 dendrites by long-term synaptic modifications: an optical imaging study with voltage-sensitive dye

  • P2-046
  • 近藤 将史 / Masashi Kondo:1,2 森田 賢治 / Kenji Morita:1 相原 威 / Takeshi Aihara:2 
  • 1:東京大院教育 / Grad. school of Education, Univ of Tokyo, Tokyo, Japan 2:玉川大院脳情報 / Grad. school of Brain Sciences, Tamagawa Univ., Tokyo, Japan 

Synaptic efficacy along dendrites is controlled by synaptic plasticity governed by presynaptic activity-induced EPSPs and postsynaptic firing-induced dendritic backpropagating action potentials (bAPs). By the way, how the synapses, which spatially discrete between the soma and dendritic spine, detect post-synaptic firing? Same as axonal spikes, bAPs are regenerative event by active conductance in dendrites. Additionally, some reports previously described that intrinsic membrane properties (e.g. spike threshold, resting membrane potential) are regulated accompanying with the synaptic plasticity. But how bAPs are influenced by these changes of membrane properties is unknown.
In this study, to investigate how long-term synaptic potentiation and depression (LTP and LTD) influence the spread of bAPs along dendrites, we measured membrane activity along hippocampal CA1 dendrites using optical imaging method with voltage-sensitive dye. As a result, the amplitudes of bAPs along dendrites were bi-directionally regulated accompanying with LTP and LTD. In other words, the amplitudes of synaptic modification and the regulation of bAPs were strongly correlated. In addition, the enhancement and suppression of bAP-spread were stable over 60 min. Moreover, the regulations of bAPs were not abolished by application of GABAa channel blocker and were abolished by NMDA channel blocker, respectively. Interestingly, in the presence of Ih channel blocker, theta-burst stimulation induced LTP was changed to LTD and also the amplitude of bAPs were suppressed.
These results suggest that the plastic change of bAP-spread along dendrites might influence the synaptic modifications at the thousands synapses on the dendrites. In other words, the bAPs might act as spatially variable meta-plastic factor for synaptic plasticity along dendrites.

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