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T. A. Münch, B. Roska; Fast Inhibitory Pathway to Ganglion Cells Involving Gap Junctions. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3619. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To characterize a novel pathway of inhibitory input to retinal ganglion cells that is important for local spatial processing of light stimuli.
Light adapted retinas were isolated from transgenic mice in which specific subsets of ganglion cells were labeled with YFP. Those cells were identified with 2-photon fluorescent imaging; their synaptic currents in response to light stimulation were recorded in voltage clamp mode, and further characterized with pharmacological agents.
We found in a genetically and morphologically identified ganglion cell type a characteristic fast inhibitory synaptic current from amacrine cells. After a light stimulus, this inhibitory current reaches the ganglion cell at least as fast as the excitatory input from bipolar cells. In addition, the amacrine cells responsible for this fast inhibitory input also appear to target the bipolar terminals of those bipolar cells which give input to the ganglion cell. As a result of this fast inhibition, ganglion cell spiking in response to high spatial frequency patterns is eliminated, and the ganglion cell spikes only for large objects. In connexin-36-k.o. mice, this characteristic fast inhibitory current is absent.
We characterized a novel inhibitory pathway in which an amacrine cell is coupled via connexin-36 containing gap junctions to bipolar cells, making the bipolar-to-amacrine cell signal transmission very fast. This allows the inhibitory input to reach the ganglion cell as fast as the excitatory input. This pathway plays an important role in the spatial processing of patterned light stimuli.
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