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A. J. Zhang, R. A. Jacoby, S. M. Wu; Modulation of Primate Horizontal Cell Receptive Fields by Light. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1157.
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© ARVO (1962-2015); The Authors (2016-present)
The objective is to determine the rod/cone inputs, spectral sensitivity and receptive field size of primate retinal horizontal cells under dark- and light-adapted conditions, and to study how background light modulates horizontal cell coupling and receptive field diameters in the primate retina.
Horizontal cells were impaled with microelectrodes filled with Neurobiotin in superfused flatmount retinas of the macaque monkey, and voltage responses to light spots of various diameters/colors or moving bars of light were recorded under dark-adapted conditions (with infrared guidance) or in the presence of 500 nm background light. Cell morphology and patterns of dye coupling were examined with a confocal microscope.
Under dark adapted conditions, H1 horizontal cells from mid-peripheral retina exhibited a spectral sensitivity curve very close to that of the green cones, and 30-minute neurobiotin injection stained over 900 H1 HC somas nearby, indicating these cells are strongly dye coupled. Light bars sweeping over the H1 receptive fields revealed that the average (±s.d.) receptive field diameter of these cells was 1,374±217 µm. The spectral sensitivity of H2 HCs suggests that these cells receive a much stronger blue cone input. 30-minute neurobiotin injection stained over 70 H2 HC somas nearby, and the average (±s.d.) receptive field diameter of these cells was 584±82 µm. When a 500 nm steady background light was introduced, the average receptive field diameter of the H1 HCs was reduced to 592±115 µm, and the average number of dye coupled cells was reduced to about half of the average number in dark-adapted retina. Addition of 200 µM Meclofenamic acid, a gap junction blocker, reduced the H1 HC receptive field diameter and number of dye coupled cells by about 10 fold.
Primate HCs in dark-adapted retina have relatively large receptive fields and extensive electrical coupling, similar to results from other vertebrate species, and light adaptation reduces HC coupling and their receptive fields. These results differ from previous reports of somewhat smaller HC receptive fields in primate retina, however, and these differences may be due to differences in the level of dark adaptation.
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