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Katelyn Sondereker, Jordan M Renna; Melanopsin ganglion cell outer retinal dendrites: A morphological analysis. Invest. Ophthalmol. Vis. Sci. 2016;57(12):4669.
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© ARVO (1962-2015); The Authors (2016-present)
Outer retinal dendrites (ORDs) originate from melanopsin ganglion cells and terminate in the outer plexiform layer (OPL), where they are colocalized with the axons of cone photoreceptor terminals. Previous research has provided anatomical evidence for synaptic transmission between the axon terminals of cone photoreceptors and ORDs. Here, we provide the first description and quantification of ORDs at different stages of mammalian retinal development.
Triple-label immunohistochemistry staining of retinal wholemounts of C57BL/6 mice at postnatal days 4, 8, 12, and 30 were imaged using confocal microscopy. The stratification of melanopsin-positive dendrites was determined by comparing their location with the presence or absence of retinal cell bodies labeled with the nuclear stains DRAQ5 or DAPI. Dendritic length of ORDs in the OPL was measured using Simple Neurite Tracer.
ORDs originate from somas of both melanopsin ganglion cells in the ganglion cell layer (GCL) and displaced melanopsin ganglion cells in the inner nuclear layer (INL). Preliminary data suggest that at each developmental age, ORDs from the somas in the GCL are shorter and have fewer branch points than those from somas in the INL. There are significantly more ORDs at P12 than at P30, with an average dendritic length of 115.800 μm (SEM ± 32.354 μm). Of the remaining ORDs at P30, the average length is 225.593 μm (SEM ± 58.628 μm).
The dendritic length of ORDs within the OPL increases throughout development. While ORDs are first seen in the postnatal retina, they persist into the adult suggesting a function for ORDs that persists throughout adulthood. Analyzing the morphology of these projections is the first step in characterizing a potential direct cone to ganglion cell circuit in the mammalian retina.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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