Phototransduction by Retinal Ganglion Cells That Set the Circadian Clock

@article{Berson2002PhototransductionBR,
  title={Phototransduction by Retinal Ganglion Cells That Set the Circadian Clock},
  author={David M. Berson and Felice A. Dunn and M. Takao},
  journal={Science},
  year={2002},
  volume={295},
  pages={1070 - 1073}
}
Light synchronizes mammalian circadian rhythms with environmental time by modulating retinal input to the circadian pacemaker—the suprachiasmatic nucleus (SCN) of the hypothalamus. Such photic entrainment requires neither rods nor cones, the only known retinal photoreceptors. Here, we show that retinal ganglion cells innervating the SCN are intrinsically photosensitive. Unlike other ganglion cells, they depolarized in response to light even when all synaptic input from rods and cones was… 
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TLDR
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TLDR
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Phototransduction in ganglion-cell photoreceptors
  • D. Berson
  • Biology
    Pflügers Archiv - European Journal of Physiology
  • 2007
TLDR
The overwhelming evidence that melanopsin serves as the photopigment in these cells is summarized and the emerging evidence that the downstream signaling cascade, including the light-gated channel, might resemble those found in rhabdomeric invertebrate photoreceptors is reviewed.
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References

SHOWING 1-10 OF 52 REFERENCES
Melanopsin in cells of origin of the retinohypothalamic tract
TLDR
It is shown that most retinal ganglion cells that project to the SCN express the photopigment melanopsin, which mediates circadian entrainment in mice.
Melanopsin-Containing Retinal Ganglion Cells: Architecture, Projections, and Intrinsic Photosensitivity
TLDR
It is shown that melanopsin is present in cell bodies, dendrites, and proximal axonal segments of a subset of rat RGCs, most likely the visual pigment of phototransducing R GCs that set the circadian clock and initiate other non–image-forming visual functions.
Spectral sensitivity of a novel photoreceptive system mediating entrainment of mammalian circadian rhythms
TLDR
The results suggest that the photoreceptive system mediating entrainment is markedly different from that involved in visual image formation, and the reciprocal relationship between intensity and duration holds for extremely long durations.
Recent developments in circadian photoreception: more than meets the eye.
TLDR
In this short article, some of the recent experimental findings that show that the absence of rod and cone photoreceptors does not block the effects of light on the circadian system are outlined and the progress to date in identifying the photopigments that may mediate the effects on the mammalian biological clock is reviewed.
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.
Sensitivity and integration in a visual pathway for circadian entrainment in the hamster (Mesocricetus auratus).
TLDR
The results suggest that the visual pathways that convey light information to the mammalian circadian pacemaker possess several unique characteristics that may make this visual system unresponsive to environmental ‘noise’ that would interfere with the entrainment of circadian rhythms to light‐dark cycles.
Light Responsiveness of the Suprachiasmatic Nucleus: Long-Term Multiunit and Single-Unit Recordings in Freely Moving Rats
TLDR
The results show that the basic light response characteristics that were observed at the multiunit level result from an integrated response of similarly behaving single units, and research at the single-unit level is a useful approach for investigating the basic principles of photic entrainment.
Melanopsin: An opsin in melanophores, brain, and eye.
TLDR
Melanopsin mRNA is expressed in hypothalamic sites thought to contain deep brain photoreceptors and in the iris, a structure known to be directly photosensitive in amphibians, and expression in retinal and nonretinal tissues suggests a role in vision and nonvisual photoreceptive tasks.
Effects of Irradiance and Stimulus Duration on Early Gene Expression (Fos) in the Suprachiasmatic Nucleus: Temporal Summation and Reciprocity
TLDR
This report provides the first demonstration that the mechanism of photon integration by the circadian system is expressed at a cellular level in the SCN, and that integration occurs over a range of 5 log units of photon number.
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