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J. Verweij, P. H. Li, O. Packer, D. M. Dacey, J. L. Schnapf; Primate Blue Cones Receive Rod Input. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3250.
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Rod stimulation evokes changes in human color perception. Direct rod input to cones through gap junctions could contribute to this effect. In primate retina, rods appear to make gap junctions with all 3 cone types, and rod signals transmitted through gap junctions have been measured in red and green cones. Are rod signals also transmitted to blue cones?
Blue cones in isolated macaque retina were targeted for whole-cell recording based on the depth and diameter of their inner segments. Identification was confirmed from measurements of spectral sensitivity.
The current response in a blue cone to a flash of light consists of 3 components: 1) a fast outward component with an action spectrum matching blue-opsin absorption, 2) a fast inward calcium current caused by feedback from horizontal cells, driven by red and green cones and 3) a slow outward component with the temporal kinetics of a rod response. This putative rod signal had the action spectrum of rhodopsin and could be evoked by rod isolating stimuli. It was selectively eliminated by rod-adapting backgrounds.
Blue cones receive rod input through rod-cone gap junctions. Quantification of the relative strength of rod input to red, green and blue cones and further modeling can determine the contribution of this pathway to color perception.
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