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Published on: October 22, 2012
Role of melanopsin in circadian responses to light
Norman F Ruby1, Thomas J Brennan, Xinmin Xie
1Department of Biological Sciences, Stanford University, Stanford, CA 94305, USA. ruby@stanford.edu
Abstract:
Melanopsin has been proposed as an important photoreceptive molecule for the mammalian circadian system. Its importance in this role was tested in melanopsin knockout mice. These mice entrained to a light/dark cycle, phase-shifted after a light pulse, and increased circadian period when light intensity increased. Induction of the immediate-early gene c-fos was observed after a nighttime light pulse in both wild-type and knockout mice. However, the magnitude of these behavioral responses in knockout mice was 40% lower than in wild-type mice. Although melanopsin is not essential for the circadian clock to receive photic input, it contributes significantly to the magnitude of photic responses.
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