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Taro Kominami, Shinji Ueno, Ayami Nakanishi, Azusa Kominami, Mineo Kondo, Takahisa Furukawa, Hiroko Terasaki; Temporal Properties of Cone ERGs of Pikachurin Null Mutant Mouse. Invest. Ophthalmol. Vis. Sci. 2016;57(3):1264-1269. doi: https://doi.org/10.1167/iovs.15-17708.
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© ARVO (1962-2015); The Authors (2016-present)
Pikachurin is an extracellular matrix-like protein located in the synaptic cleft of photoreceptors. Pikachurin null mutant (Pika−/−) mice have abnormal ON bipolar cell function. This study aimed to determine the contribution of the ON bipolar cell pathway (ON pathway) of Pika−/− mice to the flicker ERG response and, using vector analysis, identify how the contribution varies with the stimulus frequency.
Flicker ERGs were recorded from wild-type (WT), Pika−/−, and mGluR6 null mutant (mGluR6−/−) mice. The frequency of stimulation was 3.906 to 31.250 Hz. The amplitude and phase of the fundamental components were obtained by harmonic and vector model analysis. The mGluR6−/− mice were used as a model wherein the ON pathway is known to be absent.
The amplitudes of the fundamental components of the Pika−/− mice were significantly smaller than those of WT mice for stimulation frequencies between 3.906 and 17.578 Hz. The phase of the fundamental components of the Pika−/− mice was between those of the WT and mGluR6−/− mice. Vector analyses showed that the functioning of the ON pathway of Pika−/− mice was 12% to 25% of that of the WT mice at low frequencies (i.e., <15.625 Hz); however, it was reduced to noise level at frequencies >17.578 Hz.
Vector model analysis can determine the degree of contribution of the ON pathway of Pika−/− mice to flicker ERG response and may be useful for determining the retinal function in mice models with abnormalities of the ON pathway.
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