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Anneka Joachimsthaler, Tina I Tsai, Jan J Kremers; Dynamics of adaptation process to different light levels in the mouse retina studied with ERGs. Invest. Ophthalmol. Vis. Sci. 2017;58(8):5349.
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© ARVO (1962-2015); The Authors (2016-present)
To date, most studies on in vivo electroretinography in mice are performed on steady state light or dark adapted animals. In the present study, we focused on the dynamics of light and dark adaptation processes in the mouse retina.
After an initial 12 h dark adaptation animals were adapted to 25 cd/m2 white light and the responses to 6.3 cd.s/m2 flashes were recorded every 60 sec for a 15 min period. Subsequently, the mice were dark adapted again and the ERGs to 6.3 cd.s/m2 flashes were recorded every 60 sec for up to 30 min. In a second series of experiments, we recorded the changes in the responses to sinusoidal luminance modulation (12 Hz; 100% Michelson contrast) during the adaptation to a 25 cd/m2 and a 1 cd/m2 mean luminance, respectively.
flash ERGs: Significant increases of the amplitudes of b-wave (p < 0.001), PhNR (p < 0.05) and OPs (p < 0.05) were found during light adaptation. Furthermore, the implicit times of b-wave (p < 0.001) and the 2nd (p < 0.005) and 3rd OP peak (p < 0.001) decreased significantly. The changes in most parameters were completed after 10 min of light adaptation.The subsequent reduction of the background illumination led to an instantaneous decline of the ERG signal. Afterwards the amplitudes of a- (p < 0.001) and b-waves (p < 0.001) and the OPs (p < 0.001) increased during dark adaptation. Also the ratio between a- and b-wave amplitude increased strongly (p < 0.001) indicating the presence of additional adaptation processes in the OPL. Furthermore we observed a significant decrease of the implicit times of 2nd (p < 0.05) and 3rd (p < 0.001) OP peaks.sinusoidal flicker ERG: We found an interesting difference between light and dark adaptation. The fundamental phase decreased significantly during light adaptation (p < 0.001) and were constant during dark adaptation. The amplitude decreased during light adaptation (p < 0.005), but increased during dark adaptation.
Light and dark adaptation in ERG responses are highly dynamic processes that take several minutes to complete. Additionally, our data indicate that adaptation can take place at several stages in the retinal circuitry. That the response amplitude decreases to sine-wave modulation after light adaptation is at odds with the changes in the flash ERG components where the component amplitudes increase. This indicates that adaptation may be dissimilar in different signal pathways.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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