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Visual System

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

Gap junctions mediate the dendritic linkage among parvalbumin-containing GABAergic neurons both within and across the columnar space in layer 4 of the visual cortex

  • P1-174
  • 福田 孝一 / Takaichi Fukuda:1 
  • 1:熊本大院・医・形態構築 / Dept Anat and Neurobiol, Grad Sch Med Sci, Kumamoto Univ 

Accumulating evidence has indicated the presence of gap junctions between dendrites of parvalbumin (PV)-containing GABAergic neurons in the neocortex. It remains unclear, however, how gap junctions actually play roles during the neuronal computation. This is related to the difficulty in detecting neuronal gap junctions in brain tissues. Therefore, the available data on where gap junctions are incorporated in the known cortical circuit are still limited. The author previously developed a method to overcome the difficulty by a correlated CLSM-EM method that could visualize gap junction-coupled linkage of dendrites in layer 2/3 of the feline visual cortex. The present study focused on layer 4, and serial sections were double immunostained for PV and connexin36, examined in CLSM, and analyzed by Neurolucida. The linkage was not that of a simple cell-to-cell connection but constituted the dendritic reticulum formed by multiple dendrites that came close together. Reconstruction of coupled neurons revealed three types of linkage. First, PV neurons in close proximity formed mutual connections through proximally located gap junctions. Second, vertical dendrites bridged somata located at some distance inside the same columnar space. This vertical connectivity crossed the laminar border whereby the linkage was established between the bottom of layer 3 and upper layer 4 and also between layer 4 bottom and upper layer 5. The translaminar linkage was often mediated through multiple gap junctions (>5) per single pair. The third type was observed between PV neurons located in neighboring columns and linked by horizontal dendrites. Importantly, in both type 2 and 3 linkages, at least one of paired somata was located within the distance less than 100 μm from the connecting gap junction even if the other soma was more distantly located. This arrangement and previous physiological findings suggest a role of gap junctions that they transmit action potentials as EPSP-like depolarizing signals between inhibitory neurons in one direction, just like chemical excitatory synapses but without synaptic delay, both inside and across columns, whereas gap junctions among clustered neurons might mediate bidirectional synchronous signals.

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