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B Minke, S Frechter; Long-term Adaptation Largely Modifies the Quantum Efficiency of Single Photon Response in Drosophila . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1423.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Dim light stimulation induces discrete current fluctuations in most invertebrate species, which are called quantum bumps. Each bump is evoked by the absorption of a single photon. In the present study we have investigated the effect of long-term adaptation on bump frequency in response to increasing intensities of dim light. Methods: We used white-eyed Drosophila raised in the last 12 h before hatching in either complete darkness or under continuous illumination by fluorescent neon light. Bumps were measured from newly eclosed flies using patch clamp whole cell recordings. Results: Surprisingly, the frequency of bump production in dark-raised flies was about ten-fold larger than in light-raised flies. The difference in bump frequency was also reflected in the amplitude of the macroscopic light induced current (LIC) to a given light stimulus. Measurements of the intensity response relationship in dim lights also showed a significant difference between dark and light raised flies. A 10-fold shift of the intensity response function towards intense light was observed in light raised flies as opposed to dark raised flies. Analysis of the amplitude distribution of the bumps revealed no significant difference in dark and light-raised flies, thus indicating that an underscore of small bumps due to Ca2+ dependent light adaptation in light-raised flies cannot account for the above difference in bump frequency. Conclusion: Since a recent study has indicated that synthesis of Drosophila rhodopsin and arrestin do not fluctuate on a daily cycle (Hartman et al. 2001) our results suggest that quantum efficiency in Drosophila depends on the history of illumination due to a still unknown mechanism.
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