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開催日 2014/9/12
時間 11:00 - 12:00
会場 Poster / Exhibition(Event Hall B)

Dendritic integration producing directional selectivity in wind-sensitive projection interneurons

  • P2-031
  • 三谷 瑠里子 / Ruriko Mitani:1 小川 宏人 / Hiroto Ogawa:2 
  • 1:北海道大院・生命・生命システム / Biosystem Sci, Grad Sch Life Sci, Hokkaido Univ, Hokkaido, Japan 2:北海道大院・理・生物科学 / Dept Bio Sci, Fac Sci, Hokkaido Univ, Hokkaido, Japan 

Spatial distribution and balance of excitatory/inhibitory synaptic inputs on dendrites are crucial for response properties of individual neurons. Recent studies on orientation-selective neurons in visual cortex have revealed heterogeneous distribution pattern of orientation-tuned dendritic hotspots. However, it is still unclear how interaction between distribution pattern of excitatory inputs and location of inhibitory input contributes to response characteristics like directional selectivity. To address this question, we used wind-sensitive projection neuron of the cricket because individual interneurons in insect nervous system have a variable and unique dendritic shape and share various functions, unlike mammalian neurons. The wind-sensitive projection neurons have been identified as giant interneurons (GIs) in the terminal abdominal ganglion of the cricket. The GIs directly receive excitatory synaptic inputs from the sensory afferents of mechanoreceptor neurons having various directional sensitivities. And, some types of GIs also receive inhibitory inputs from local interneurons, presumably. The GIs displays distinct directional selectivity, but the relationship between dendritic distribution of the excitatory and inhibitory synaptic inputs and their directional selectivity is unknown. To clarify the input-distribution on dendrites of GIs, we examined directional tuning in dendritic Ca2+ responses to air current from various angles and effects of GABAA receptor antagonist, PTX. In GI 8-1, dendritic Ca2+ response at distal branch differed in directional selectivity from the Ca2+ response at proximal dendrite and voltage response. In contrast, the Ca2+ response in all over the dendrite of GI 10-2 were similar in directional selectivity to the voltage response. These results indicated that spatial heterogeneity of excitatory inputs in their directional sensitivity depended on the type of GIs. Furthermore, block of the inhibitory inputs with PTX made the directional selectivity to be blunt. Probably, inhibitory inputs play an important role in forming of the directional tuning property specific to the each type of GIs.

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