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Z. Chen, Z. Yin; More Morphological and Functional Survival of Melanopsin-Containing Retinal Ganglion Cells in Retinal Degeneration. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5025.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the morphological properties and quantitative changes of melanopsin-containing retinal ganglion cells (mRGCs), and to compare voltage-activated sodium and potassium currents of mRGCs in RCS and Control rats during retinal degeneration, so to explore the pathomechanisms of inner retinal neuronal degeneration following the loss of photoreceptors.
Retinal mount and cryosections were stained with anti-melanopsin at P21, P60d and P90d RCS and Control rats. The distribution, morphology and density of mRGCs were investigated. Retrograde labeling with Fluorogold in superachiasmatic nucleus (SCN) was performed to indentify mRGCs. Retinal slices were prepared and labeled cells were recorded using whole-cell patch clamp under infrared-fluorescence microscope. The voltage-activated sodium and potassium currents were recorded under voltage clamp mode with the application of channel blockers. Action potentials (APs), current amplitude, density and I-V curves were compared between RCS and Control rats. The properties of mRGCs also were compared with RGCs.
With the loss of photoreceptors the number of total retinal ganglion cells decreased significantly, nevertheless more mRGCs survived. The distribution, morphology of soma and processes of mRGCs in RCS rat was almost the same with that in Control rats during postnatal stages. The ratio of mRGCs to total RGCs in RCS rats is significantly higher than that in Control rats at late stage of RD. mRGCs were labeled successfully with injection in SCN. Whole cell recording was accomplished in both RGCs and mRGCs. Single, transient and sustained firing was recorded in RGCs at P21d, but later stage is transient and sustained firing. The most is transient in mRGCs. During postnatal development there were no significant differences in the amplitude and density of sodium and potassium current of mRGCs in RCS and Control rats. However, at late stages of retinal degeneration, only part of RGCs could be evoke to action potential, and the amplitude and density of sodium currents decreased dramatically in RCS rats.
Inner retinal neurons including RGCs were secondarily degenerated, nevertheless mRGCs appeared more resistant to RD. The results indicated that mRGCs may possess certain unique property and be less susceptible to RD than other subpopulations of RGCs because of being able to perceive light directly. The primary exploration on death of mRGC and survival of mRGCs provide the clues for neural protection and function rebuilding.
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