Comparison of photopic negative response (PhNR) between focal macular and full-field electroretinograms in monkeys
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To compare the 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 cynomolgus monkeys under identical stimulus and recording conditions except for which area of the retina was illuminated. The luminance and duration of red flash stimuli were varied in the presence of steady blue background illumination. These ERGs were recorded before and after intravitreal injection of tetrodotoxin (TTX).
Several differences were identified between the focal macular and full-field ERGs, including: (1) The PhNR/b-wave amplitude ratio was higher in the focal macular 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. For both macular and full-field stimulation conditions, (1) PhNR amplitude generally increased with increasing stimulus luminance; (2) PhNR implicit time was independent of the stimulus luminance; (3) PhNR amplitude and implicit time increased with increasing stimulus duration up to 50 ms, while a further increase in stimulus duration produced no change in amplitude or implicit time; and (4) PhNR amplitude was selectively attenuated by TTX.
Both the focal macular and full-field PhNRs reflect the functional properties of the inner retina including the retinal ganglion cells (RGCs). Relative to the b-wave, the contribution is weighted more heavily in the focal macular than in the full-field PhNR. Furthermore, these results support the idea that the focal macular PhNR can be an indicator of the function of the macular RGCs.
KeywordsPhotopic negative response Retinal ganglion cells Monkey Focal macular ERG Tetrodotoxin
The authors thank Hidetaka Kudo of Mayo Corporation for technical assistance.
Compliance with ethical standards
Conflict of interest
Human and animal rights
All applicable international, national, and/or institutional guidelines for the care and use of animals were followed. All procedures performed in studies involving animals were in accordance with the ethical standards of the Institutional Animal Care and Use Committee of Daiichi Sankyo Co. Ltd. This article does not contain any studies with human participants performed by any of the authors.
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