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Visual System

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

Photoreceptor ribbon synapse contributes to the spatiotemporal frequency property of late-phase optokinetic responses in mice

  • P1-167
  • 杉田 祐子 / Yuko Sugita:1,2,5 荒木 章之 / Fumiyuki Araki:3,4 茶屋 太郎 / Taro Chaya:1,2,3 河野 憲二 / Kenji Kawano:5 古川 貴久 / Takahisa Furukawa:1,2,3 三浦 健一郎 / Kenichiro Miura:5 
  • 1:大阪大・蛋白質研・分子発生学 / Lab. Mol & Dev Biology, Protein Inst, Osaka Univ, Osaka, Japan 2:科学技術振興機構・CREST / JST, CREST, Osaka, Japan 3:大阪バイオサイエンス研・発生生物学 / Dept. Dev Biology, OBI, Osaka, Japan 4:東京大・医・眼科学 / Dept.Ophthalmology, Univ Tokyo, Tokyo, Japan 5:京都大院・医・認知行動脳科学 / Dept. Integ Brain Sci, Grad Sch. Med, Kyoto Univ, Kyoto, Japan 

There is a specialized synaptic structure called ribbon synapse in the outer plexiform layer of the retina where visual signals are transmitted from photoreceptors to bipolar and horizontal cells. This structure is thought to promote high-efficiency signal transmission, but its role in visual function is unclear. In the present study, we examined initial and late phases of the optokinetic responses (OKRs) of Pikachurin-null mutant mice, which have improper formation of the photoreceptor ribbon synapse, to understand its role in visual function. The initial phase was examined by measuring the open-loop eye velocity of the OKRs to sinusoidal grating patterns of various spatial frequencies moving at various temporal frequencies for 0.5s. The mutant mice showed significant initial OKRs with a spatiotemporal frequency tuning that was similar to wild-type mice, although the amplitude was smaller. The observation of transient ocular responses elicited by two-frame animations with inter-stimulus intervals, during which the display was of the same mean luminance, also revealed no noticeable difference between the mutant and wild type mice, confirming similar temporal characteristics of the visual process underlying the initial OKRs. Finally, the late phase of the OKRs was examined by measuring the slow phase eye velocity of the optokinetic nystagmus induced by sinusoidal gratings of various spatiotemporal frequencies moving for 30s. We found that the optimal spatial and temporal frequencies of the mutant mice (spatial frequency, 0.11 cpd; temporal frequency, 0.74 Hz) were both lower than wild-type mice (spatial frequency, 0.16 cpd; temporal frequency, 1.91 Hz). These results suggest that the photoreceptor ribbon synapse contributes to the spatiotemporal frequency tuning of visual processing along the ON pathway by which the late phase of OKRs is mediated.

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