Role of Melanopsin in Circadian Responses to Light

@article{Ruby2002RoleOM,
  title={Role of Melanopsin in Circadian Responses to Light},
  author={Norman F. Ruby and Thomas J. Brennan and Xinmin Xie and Vinh H. Cao and Paul Franken and H. Craig Heller and Bruce F. O’Hara},
  journal={Science},
  year={2002},
  volume={298},
  pages={2211 - 2213}
}
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… 
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References

SHOWING 1-10 OF 21 REFERENCES
Regulation of mammalian circadian behavior by non-rod, non-cone, ocular photoreceptors.
TLDR
Neither rods nor cones are required for photoentrainment, and the murine eye contains additional photoreceptors that regulate the circadian clock.
Phototransduction by Retinal Ganglion Cells That Set the Circadian Clock
TLDR
It is shown that retinal ganglion cells innervating the SCN are intrinsically photosensitive, and depolarized in response to light even when all synaptic input from rods and cones was blocked.
Preservation of light signaling to the suprachiasmatic nucleus in vitamin A-deficient mice
TLDR
The data suggest that a non-opsin pigment is the primary circadian photoreceptor in the mouse.
Differential regulation of mammalian period genes and circadian rhythmicity by cryptochromes 1 and 2.
TLDR
It is demonstrated that Cry1 and Cry2 are required for the normal expression of circadian behavioral rhythms, as well as circadian rhythms of mPer1 and mPer2 in the SCN.
Functional redundancy of cryptochromes and classical photoreceptors for nonvisual ocular photoreception in mice.
TLDR
Data indicate that classical opsins and cryptochromes serve functionally redundant roles in the transduction of light information to behavioral modulation and suggest a pleomorphic role for cryptochrome in both photoreception and central clock mechanism.
Action Spectrum for Melatonin Regulation in Humans: Evidence for a Novel Circadian Photoreceptor
TLDR
The results suggest that, in humans, a single photopigment may be primarily responsible for melatonin suppression, and its peak absorbance appears to be distinct from that of rod and cone cellphotopigments for vision.
Retinal projections in mice with inherited retinal degeneration: Implications for circadian photoentrainment
TLDR
Pseudorabies virus is used as a neuroanatomical tract tracer in mice to address a series of questions about which retinal cells mediate circadian responses to light and the nature of the retinohypothalamic projection.
...
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