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Clement Afari, Daphne L McCulloch, Chung Ki Fung, Akshay Gurdita, Vivian Choh; Assessment of the photopic negative response in full-field electroretinogram in optic nerve-sectioned young chick eyes. Invest. Ophthalmol. Vis. Sci. 2017;58(8):5348.
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The photopic negative response (PhNR) is known to reflect the functions of retinal ganglion cells in mammals but its origin in non-mammalian species is established. This study was undertaken to determine whether the PhNR from optic nerve-sectioned young White Leghorn (Gallus gallus domesticus) chicks reflect RGCs functions and also describe the nature of longitudinal PhNRs.
Full-field photopic electroretinograms (ERGs) were recorded bilaterally from hatchling chicks (N = 4) before optic nerve section (ONS) on one eye and sham surgery on the fellow control eye. ERGs were recorded again on days 3, 5 and 7 post-ONS. Stimuli were 4 ms red (λ = 650 nm) flashes in increasing half log steps from 0.1 to 5 cd.s/m2 on rod suppressing blue (λ = 462 nm) background (30 cd/m2). The a-waves, b-waves and PhNRs were measured, with the latter calculated relative to the b-wave.
ERGs were clearly recordable from all eyes showing the expected luminance-response functions, with saturation at log 3 cd.s/m2. At all luminance levels, PhNR amplitudes for control eyes (63.77 ± 4.81 µV) were similar (p = 0.16) to those of ONS eyes (54.49 ± 4.09 µV). The a-wave and b-wave amplitudes were also not different between the eyes for all time points and luminance levels (p = 0.31). Differences in ERG amplitudes with maturation were not significant (p ≥ 0.14).
Although the PhNR of the ERG is diminished in conditions affecting ganglion cell function in mammalian models, our data do not support this conclusion in young chicks.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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