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J. Pang, F. Gao, S.M. Wu; Light–Evoked Current Responses of Morphologically–Identified Amacrine Cells in Dark–Adapted Mouse Retina . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3459.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The objective is to determine the sensitivity, polarity and waveform of light–evoked cation and chloride currents of various morphological types of amacrine cells (ACs) in the mammalian retina. Methods: Light–evoked excitatory cation currents (ΔIC) and inhibitory chloride currents (ΔICl) of ACs in dark–adapted mouse retinal slices were studied by whole–cell voltage clamp recording techniques, and cell morphology was revealed by Lucifer yellow fluorescence with a confocal microscope. Results: In a total of 72 ACs, more than 80% exhibited a sustained or transient inward ΔIC at light onset, about 10% showed a sustained outward ΔIC or transient inward ΔIC at light offset, and the remaining displayed transient inward ΔIC at both light onset and offset. All ACs with narrow dendritic trees distributed in both sublamina A and B of the inner plexiform layer (IPL) had an inward ΔIC, and more than half of these cells exhibited typical AII AC morphology, response waveform and light sensitivity reported in our earlier study. The remaining of such cells exhibited more spontaneous EPSCs, lower light sensitivity and more pronounced ΔICl. ACs with dendrites ramified in sublamina A exhibited either a transient inward ΔIC at light offset or a sustained outward ΔIC during the light stimuli, those with dendrites in sublamina B had a sustained inward ΔIC at light onset, and ACs with dendrites ramifying in the middle portion of the IPL exhibited a transient inward ΔIC at light onset and offset. ΔICl in most ACs was small (as compared with the ΔICl in salamander ACs) and in some cells they were masked by ΔIC from other ACs in the coupled network (e.g. AIIACs). Spontaneous IPSCs were observed in about 30–40% of ACs. Conclusions: There is a wide variety of morphological types of ACs in the mouse retina. Most of these exhibit distinguishable light response characteristics that correlate with patterns of dendritic ramification in the IPL. However, some ACs with very similar morphology have different light responses, while other ACs with similar light responses have different morphology. Hence AC classification by morphology alone may not be always appropriate.
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