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V. P. Connaughton, R. Nelson; Light Responses From Presumed Horizontal and Amacrine Cells in Zebrafish Retina. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5957.
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© ARVO (1962-2015); The Authors (2016-present)
To identify different spectral classes of horizontal and amacrine cells in the zebrafish retina based on light responses
Retinal neurons were penetrated using sharp, high impedance (~100-300MOhm) microelectrodes in light-adapted, superfused zebrafish retina-eyecup wholemounts. Electrodes were filled with 3M KCl; oxygenated MEM was the extracellular solution. Light responses were obtained in response to full-field stimuli with wavelengths ranging from red (650nm) to ultraviolet (330nm), to selectively stimulate the different cone types.
Two groups of horizontal cells were identified. Presumed L-type cells were hyperpolarized by light and response polarity did not change with stimulus wavelength. These were the most abundant responses recorded. Most of these cells (n=7) responded maximally to red (650nm) and/or yellow (575nm) stimuli, indicating they are red-cone preferring units. Others (n=4) responded maximally to blue (410-490nm) and UV (370nm) stimulation. A third group was spectrally indifferent (n=6), as all stimulating wavelengths elicited light responses of similar amplitude. Within these spectral classes, response waveforms were either sustained, more transient at light ON, or more transient at light OFF. Overall, the responses of these cells were diverse, as waveform and/or response amplitude changed with stimulus wavelength and/or intensity. Responses of presumed C-type horizontal cells changed polarity with either stimulus wavelength or brightness. Both biphasic and triphasic responses were identified. As with L-type cells, C-type cells also had complicated waveforms. Most presumed amacrine cells displayed transient ON/OFF depolarizing light responses. In three of these cells, this transient response, observed during yellow light stimulation, became sustained in response to other stimulating wavelengths. In the remaining cells, response waveform did not change with wavelength of stimulation. Rather, the amplitude of response changed with either stimulus wavelength or brightness, particularly in response to blue and/or UV light. Two other amacrine-like responses were identified: a transient OFF response and a transient ON type with an AII-amacrine-like response.
Light responses of presumed horizontal and amacrine cells in the zebrafish retina are complex, showing changes in amplitude and/or waveform of response with different stimulus wavelengths. This suggests there are many spectral classes of horizontal cells, including many L-type units and C-type units, as well as distinct spectral types of amacrine cell.
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