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Y. Yang, C.-C. Chiao; Dynamic Tracer Coupling of Amacrine Cells in the Rabbit Retina. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3048. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Many types of amacrine cells are coupled by gap junctions. Previous studies using Neurobiotin as a tracer have revealed numerous static coupling patterns, and the corresponding fluorescent intensities have been used to estimate dynamic coupling among different cell types. In this study, we used a fluorescent tracer (PoPro-1) to directly visualize the coupling patterns, and characterized the spatial and temporal dynamics of the couplings in amacrine cells of the rabbit retina.
The AII and polyaxonal cells from adult New Zealand White rabbits were iontophoretically injected with PoPro-1. Immediately after tracer injection, a time-lapse live imaging of the targeted amacrine cell and its surrounding cells was taken using a CCD camera driven by the MetaMorph software. The z-stack images were collected above and below the focal plane of the PoPro-1 injected cell using a z-motor at each time lapse to spatially localize the somata of coupled cells in the retina.
Consistent with previous studies, we found that AII cells coupled to other AII cells and bipolar cells, and AII-AII coupling is faster than AII-bipolar coupling. Polyaxonal cells were coupled to ganglion cells, amacrine cells, as well as bipolar cells in some cases. After the initial period of tracer diffusion, the number of coupled cells in AII cell coupling network continues to increase, while the number of coupled cells in polyaxonal cell coupling network ceases to increase. In general, the distance of coupled cells from the injected cell was proportional to the injection time, but was inversely related to the fluorescent intensity.
Our results provide a direct support of spatial and temporal coupling patterns in AII cells and in polyaxonal cells previously derived from the tracer diffusion model indirectly. The time-lapse recording of the fluorescent intensity after PoPro-1 injection thus allows us to dynamically characterize the strength of gap junctions among various cell types and the direction of signal flow in the living retina.
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