Melanopsin-Containing Retinal Ganglion Cells: Architecture, Projections, and Intrinsic Photosensitivity

@article{Hattar2002MelanopsinContainingRG,
  title={Melanopsin-Containing Retinal Ganglion Cells: Architecture, Projections, and Intrinsic Photosensitivity},
  author={Samer Hattar and Hsi Wen Liao and M. Takao and David M. Berson and King-Wai Yau},
  journal={Science},
  year={2002},
  volume={295},
  pages={1065 - 1070}
}
The primary circadian pacemaker, in the suprachiasmatic nucleus (SCN) of the mammalian brain, is photoentrained by light signals from the eyes through the retinohypothalamic tract. Retinal rod and cone cells are not required for photoentrainment. Recent evidence suggests that the entraining photoreceptors are retinal ganglion cells (RGCs) that project to the SCN. The visual pigment for this photoreceptor may be melanopsin, an opsin-like protein whose coding messenger RNA is found in a subset of… 

Central projections of melanopsin‐expressing retinal ganglion cells in the mouse

TLDR
Staining patterns after monocular enucleation revealed that the projections of these cells are overwhelmingly crossed except for the projection to the SCN, which is bilaterally symmetrical, and that other ganglion cells do contribute at least some retinal input to these targets.

Melanopsin is expressed in PACAP-containing retinal ganglion cells of the human retinohypothalamic tract.

TLDR
Given the expression of melanopsin in PACAP-containing RGCs of the human RHT, this photoreceptor is a likely first base in the chain of events leading to photoentrainment of both normal and blind people.

A Broad Role for Melanopsin in Nonvisual Photoreception

TLDR
The results suggest that melanopsin expression defines a subset of RGCs that play a broad role in theregulation of nonvisual photoreception, providing collateralized projections that contribute to circadian entrainment, negative masking, the regulation of sleep-wake states, and the pupillary light reflex.

Immunohistochemical evidence of a melanopsin cone in human retina.

TLDR
The presence of melanopsin in human cones suggests image and non-image-forming roles in visual responses at both the cone input and ganglion cell output stages and their involvement in a broad spectrum of irradiance detection functions in the visual system.

Melanopsin and non-melanopsin expressing retinal ganglion cells innervate the hypothalamic suprachiasmatic nucleus

TLDR
It appears that the rod/cone system of photoreceptors may provide signals to the SCN circadian system independent of intrinsically light-sensitive melanopsin ganglion cells.

Melanopsin Regulates Visual Processing in the Mouse Retina

Melanopsin and rod–cone photoreceptive systems account for all major accessory visual functions in mice

TLDR
The rod–cone and melanopsin systems together seem to provide all of the photic input for these accessory visual functions such as pupillary light reflex and circadian photo-entrainment.

Melanopsin, the photopigment of intrinsically photosensitive retinal ganglion cells

Melanopsin (gene symbol: Opn4) is the G protein-coupled photopigment that confers photosensitivity upon intrinsically photosensitive retinal ganglion cells (ipRGCs). ipRGCs are the third class of

Melanopsin—Shedding Light on the Elusive Circadian Photopigment

TLDR
Although melanopsin is clearly the leading candidate for the elusive photopigment of the circadian system, further research is needed to resolve the mystery posed by its absorbance spectrum and to fully elucidate its role in circadian photoentrainment.
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