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Ji-Jie Pang, Fan Gao, Samuel M Wu; Light responses and amacrine cell modulation of morphologically-identified retinal ganglion cells in the mouse retina. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1857.
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© ARVO (1962-2015); The Authors (2016-present)
To elucidate how narrow-field (glycinergic) amacrine cells modulate light responses of various types of retinal ganglion cell in the mammalian retina.
We recorded RGCs under whole-cell patch-clamp and cell-attached modes and analyzed light-evoked spike responses, cation currents (ΔIC) and chloride currents (ΔICl) of over 100 morphologically-identified retinal ganglion cells (RGCs) in dark-adapted mouse retina. The morphology of recorded RGCs was examined with the immunofluorescence and confocal microscopy.
We found there are at least 14 functionally- and morphologically-distinct types of RGCs. These cells can be divided into 5 groups based on their patterns of spike response to whole field light steps (SRWFLS groups), a RGC identification scheme commonly used in studies with extracellular recording techniques. We also found that all RGCs in the mouse retina express strychnine-sensitive glycine receptors, and receive light-elicited chloride current (ΔICl) accompanied by a conductance increase from narrow-field, glycinergic amacrine cells. As the dark membrane potential of RGC are near the chloride-equilibrium potential, mouse RGCs’ spike responses are mediated primarily by bipolar cells inputs, and modulated by “shunting inhibition” from narrow-field amacrine cells. Analysis of strychnine actions on light-evoked cation current ΔIC (bipolar cell inputs) in RGCs suggests that narrow-field amacrine cells modulate RGCs by sending ON-OFF crossover feedback signals to presynaptic bipolar cell axon terminals via sign-inverting glycinergic synapses, and the feedback signals are synergistic to the bipolar cell light responses.
Narrow-field amacrine cells enhance light-evoked bipolar cell inputs to RGCs by presynaptic “synergistic addition”, in addition to postsynaptic “shunting inhibition”.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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