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N Tian; Development and Intensity-dependent Regulation of Retinal Ganglion Cell (RGC) Transient Responses . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2977.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:One of the remarkable differences between the light responses of inner retinal neurons (amacrine and ganglion cells) and outer retinal neurons (photoreceptors, horizontal and bipolar cells) is that the light responses of inner retinal neurons have both transient and sustained components. The synaptic mechanisms with which retina converts sustained light responses in outer retina into transient light responses in inner retina have not been identified. In this study, I examined developmental regulations and stimulus intensity dependence of RGC transient ON responses in mouse retina. Methods:Mouse RGC light responses evoked by a series of light stimuli were recorded using a multielectrode array system, which enabled me to sample spike responses from several dozen RGCs at a time. Cell types were classified based on the magnitude and kinetics of their responses to the onset and offset of light step. Results:The number of transient RGCs is developmentally regulated. There are only 30% of RGCs which receive inputs from ON bipolar cells respond transiently to light step around the time of eye opening (P10-15). At P30, however, the number of transient ON RGCs increased to 60%. The cell types are also light intensity sensitive. There are two types of transient cells. One type of cells responds transiently to light ON at both low and high intensities. Another type of cells responds transiently to light ON at low intensity light stimuli. Their light responses become sustained at higher intensity stimuli. There are slightly more than 50% of sustained RGCs have transient light responses at low intensity stimulus in both young and adult animals. Conclusion:These results demonstrated that there are at least two different mechanisms control RGC transient light responses. One is light intensity independent and another is light intensity dependent. The light intensity independent mechanism matures at least one week (P15) after the synaptic connections between bipolar and ganglion cells are established (∼P7-9). However, the light intensity dependent mechanism is not developmentally regulated after eye opening.
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