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Whitney M. Cleghorn, Elviche Lenou, Xiufeng Song, Sergey A. Vishnivetskiy, Jungwon Seo, Eugenia V. Gurevich, Vsevolod V. Gurevich; Reduced Arrestin in the OS Slows Down Photoresponse Recovery in Rods. Invest. Ophthalmol. Vis. Sci. 2011;52(14):32.
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© ARVO (1962-2015); The Authors (2016-present)
To determine how arrestin availability affects the rate of recovery in rod photoreceptors.
We used two-flash ERG to determine the rate of rod recovery in vivo.
Mice expressing arrestin at various levels: 4% (Tr-4Arr-/-), 12% (Tr-12Arr-/-), 50% (Arr+/-), and 100% of wild-type (WT), were tested by two-flash ERG with the first (desensitizing) flash at 160, 400, 1000, and 2500 photons/rod. The level of recovery was determined by the response to a probe flash of 4500 photons/rod delivered at variable intervals after the desensitizing flash. We showed that recovery in WT retinas progressively slows with increasing intensity of the initial flash. Time of half recovery is ~ 2.5-fold longer after the highest flash intensity (2500 photons/rod) than after the lowest (160 photons/rod). Mice expressing arrestin at 50% and 12% of the normal level were not statistically different from WT mice at any light intensity tested. Interestingly, the mice expressing the lowest level of arrestin (4%) had a dramatically slower recovery than the other three genotypes at all intensities. In these mice, the time of half recovery increased ~28 fold when tested with the highest flash intensity, in contrast to ~2.5 in other animals. Even after the dimmest desensitizing flash, the rate of recovery of Tr-4Arr-/- rods was two times slower than in other lines.
Our data show that arrestin expression between 100% and 12% of WT is sufficient for rapid recovery at different light levels. Gradual slowing of recovery with increasing intensity of the first flash observed in Tr-12Arr-/-, Arr+/-, and WT animals becomes dramatic with limited arrestin in Tr-4Arr-/- mice. This suggests that there is a threshold of arrestin expression between 4% and 12% of WT for transition from near normal to abnormally slow photoresponse recovery.
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