title: Pikachurin Protein Required for Increase of Cone Electroretinogram B-Wave during Light Adaptation.
abstract: In normal eyes, the amplitude of the b-wave of the photopic ERGs increases during light adaptation, but the mechanism causing this increase has not been fully determined. The purpose of this study was to evaluate the contribution of receptoral and post-receptoral components of the retina to this phenomenon. To accomplish this, we examined the ERGs during light adaptation in Pikachurin null-mutant (Pika -/-) mice, which have a misalignment of the bipolar cell dendritic tips to the photoreceptor ribbon synapses. After dark-adaptation, photopic ERGs were recorded from Pika -/- and wild type (WT) mice during the first 9 minutes of light adaptation. In some of the mice, post-receptoral components were blocked pharmacologically. The photopic b-waves of WT mice increased by 50% during the 9 min of light adaptation as previously reported. On the other hand, the b-waves of the Pika -/- mice decreased by 20% during the same time period. After blocking post-receptoral components, the b-waves were abolished from the WT mice, and the ERGs resembled those of the Pika -/- mice. The extracted post-receptoral component increased during light adaptation in the WT mice, but decreased for the first 3 minutes to a plateau in Pika -/- mice. We conclude that the normal synaptic connection between photoreceptor and retinal ON bipolar cells, which is controlled by pikachurin, is required for the ERGs to increase during light-adaptation. The contributions of post-receptoral components are essential for the photopic b-wave increase during the light adaptation.
authors.affiliation: Department of Ophthalmology, Nagoya University Graduate School of Medicine, Nagoya, Aichi, Japan.
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Nagaya
authors.affiliation: Department of Ophthalmology, Nagoya University Graduate School of Medicine, Nagoya, Aichi, Japan.
authors.forename: Shinji
authors.initials: S
authors.lastname: Ueno
authors.affiliation: Department of Ophthalmology, Nagoya University Graduate School of Medicine, Nagoya, Aichi, Japan.
authors.forename: Taro
authors.initials: T
authors.lastname: Kominami
authors.affiliation: Department of Ophthalmology, Nagoya University Graduate School of Medicine, Nagoya, Aichi, Japan.
authors.forename: Ayami
authors.initials: A
authors.lastname: Nakanishi
authors.affiliation: Department of Ophthalmology, Mie University Graduate School of Medicine, Tsu, Mie, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Koyasu
authors.affiliation: Department of Ophthalmology, Mie University Graduate School of Medicine, Tsu, Mie, Japan.
authors.forename: Mineo
authors.initials: M
authors.lastname: Kondo
authors.affiliation: Laboratory for Molecular and Developmental Biology, Institute for Protein Research, Osaka University, Suita, Osaka, Japan; JST, CREST, Suita, Osaka, Japan.
authors.forename: Takahisa
authors.initials: T
authors.lastname: Furukawa
authors.affiliation: Department of Ophthalmology, Nagoya University Graduate School of Medicine, Nagoya, Aichi, Japan.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Terasaki
mesh_terms: D000221:Adaptation, Ocular; D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D004596:Electroretinography; D058787:GABA-A Receptor Antagonists / Q000494:pharmacology; D051379:Mice; D018345:Mice, Knockout; D023421:Models, Animal; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D010775:Photic Stimulation; D017949:Retinal Cone Photoreceptor Cells / Q000187:drug effects / Q000502:physiology*
chemical_list: D002352:Carrier Proteins; D058787:GABA-A Receptor Antagonists; D009419:Nerve Tissue Proteins; C553232:pikachurin protein, mouse; D001640:Bicuculline