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Ye Long, Stephen L Mills; Properties of novel types of transient On ganglion cells in the rabbit retina. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3576.
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© ARVO (1962-2015); The Authors (2016-present)
The diversity of retinal ganglion cells has been explored based on their physiological and morphological properties for many years, most fully in the rabbit and mouse retinas. Early estimates of about 15 types now appear to be perhaps half the true number. Our purpose is to further characterize lesser-known ganglion cell types in the rabbit retina. Examination of the different ganglion cell types will help us further understand the visual pathways that underline vision. Here, we focus on On transient ganglion cells.
Using isolated retinas from New Zealand white rabbits, medium somas visualized with acridine orange and whose border between cytoplasm and nuclei bisect the cell were recorded via loose patch. Spiking responses to structured stimuli projected onto the photoreceptor layer of the whole-mount retina were used to characterize cells. Injected Neurobiotin visualized with streptavidin-Cy3 revealed cell morphologies. ChAT antibody was used to accurately determine the stratification depth.
Two new transient On cells could be distinguished morphologically by the soma and dendritic tree sizes, branching patterns, and stratification levels. One showed medium size somas and dendritic trees with curving terminal branches and ramified between the On and Off ChAT bands. Temporal responsiveness was slow (2 Hz) in control and increased by GABA and glycine antagonists (10 Hz). The mGluR6 agonist APB decreased spiking rates, but didn’t completely abolish light responses. The effects of kainate and NMDA receptor antagonists were slight, suggesting potential input from the Off pathway. The morphology of this cell may match that of the physiologically uncharacterized G2 ganglion cell (Rockhill et al. 2002). A second, thorny ganglion cell ramifying below the On ChAT band was also transient and appears to be previously undescribed. Neither cell type was directionally selective.
Roska et al. (2006) listed 3 types of On transient ganglion cell, one called On parasol (probably the transient ON DS ganglion cell), an On α ganglion cell, and an ON bistratified cell. Our work suggest the presence of 5 types of On transient and 4 types of Off transient ganglion cell. It is presently unclear why the visual system would require this number of types, which overlap in spatial and temporal sensitivity. More subtle differences in coding and spiking behavior of these cells are being investigated.
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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