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Chad R. Jackson, Laurel A. Young, Douglas G. McMahon; Photoperiod Affects The Electroretinographic Response In Mice. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2720.
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In mammals, the retina is the sole light-sensing tissue that transduces photic input into electrical signals that the brain organizes into perception. In addition to light being processing by the retina, research has shown that light history can affect retinal function and development due to changes in lighting environment and photoperiod. Previous studies indicate that humans with seasonal affective disorder or winter depression have altered retinal function. Therefore, we hypothesize that mice subject to short photoperiods will have altered retinal functioning when compared to mice subject to long photoperiods as measured by the electroretinogram.
Scotopic and photopic electroretinogram (ERG) responses from C57/BL/6 mice bred and raised on short (8 hrs light:16 hrs dark) or long (16 hrs light:8 hours dark) photoperiods were recorded following overnight dark-adaption (18 and 14 h, respectively). Mice were handled under dim red-filtered light, anesthetized with ketamine/xylazine (70mg/kg and 7mg/kg, respectively), placed in a LKC UTAS BigShot ganzfeld, and core body temperature was maintained at 37 degrees Celsius. Scotopic ERG responses were recorded by exposing dark-adapted mice to light flashes of increasing intensity. After the final scotopic measurement, mice were exposed to a rod-saturating background light (40 cd/m2) for 10 min, then photopic ERG responses were recorded by exposing the mouse to 20 bright light flashes (~100 cd-s/m2) which were averaged into one wave form.
Scotopic a- and b-wave responses were significantly affected by photoperiod. Post hoc statistical testing revealed that scotopic ERG responses for both a- and b-waves were significantly reduced in short photoperiod mice when compared to long photoperiod mice ( p = 0.004 and p = 0.001). Comparative photopic b-wave responses between short and long photoperiods displayed no statistical difference; however, short photoperiod mice show a noticeable decrease in photopic b-wave amplitude response.
Photoperiod significantly affects scotopic retinal function; however, differential effects on the retina’s ability to adapt and respond to changes in background illumination were not detected.
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