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Junzo Kinoshita, Shunsuke Takada, Noriaki Iwata, Yoshiro Tani; Comparison of photopic negative response (PhNR) between focal macular and full-field electroretinograms in monkeys. Invest. Ophthalmol. Vis. Sci. 2016;57(12):5757.
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© ARVO (1962-2015); The Authors (2016-present)
To compare the response characteristics of the photopic negative response (PhNR) between the focal macular and full-field electroretinograms (ERGs) in monkeys.
Both focal macular and full-field photopic ERGs were recorded in four anesthetized cynomolgus monkeys under the essentially identical stimulus and recording conditions except for illuminated area of the retina. The luminance and duration of red flash stimuli were varied in the presence of steady blue background illumination. These ERGs were also recorded in the same manner after intravitreal injection of tetrodotoxin (TTX), which blocks Na+-dependent action potentials that occur in the retinal ganglion cells (RGCs).
Following similarities between the focal macular and full-field PhNRs were observed: 1) the amplitude generally increased with increasing stimulus luminance; 2) the implicit time was independent of the stimulus luminance and basically constant for long-duration flashes; 3) both the amplitude and implicit time increased with increasing stimulus duration up to 50 ms, but further increase in stimulus duration produced no increase in the amplitude or implicit time; and 4) the PhNR was markedly attenuated by intravitreal TTX. On the other hand, differences were also identified as described below: 1) the PhNR/b-wave amplitude ratio was higher in the focal macular ERGs than in the full-field ERGs; and 2) the stimulus threshold of the focal macular PhNR was lower than that of the full-field PhNR.
Our results suggest that the focal macular PhNR is a local homologue of the full-field PhNR and is generated from the inner retinal neurons including the RGCs in the macula. They also suggest that functional contribution of the inner retina is greater in the focal macular ERG than in the full-field ERG in primates.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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