Recording Focal Macular Photopic Negative Response (PhNR) from Monkeys

¹ Department of Ophthalmology, Nagoya University Graduate School of Medicine, Nagoya, Japan

^* To whom correspondence should be addressed. E-mail: kondomi{at}med.nagoya-u.ac.jp.

	Abstract

Purpose. To record the photopic negative response (PhNR) of the focal electroretinograms (ERGs) from the macula of monkeys, and to study the properties of the focal macular PhNRs. Methods. Focal macular ERGs were recorded from five rhesus monkeys using a modified infrared fundus camera, in which a red stimulus spot on a blue background illumination were incorporated. The effects of different stimulus intensities and durations presented on a steady blue background of 100 scot cd/m² on the focal macular PhNRs were investigated. Focal macular PhNRs were also recorded before and after an intravitreal injection of tetrodotoxin (TTX). Results. Based on the results of attempting to elicit focal ERG recorded from a photocoagulated retinal site, we concluded that the responses were focal when the luminance of the red stimulus spot was 55 phot cd/m² and presented on a steady blue background of 100 scot cd/m². The amplitude of the focal macular PhNR increased with increasing stimulus intensities, and was larger than that of the b-wave for all stimulus intensities. The amplitude of the focal macular PhNR was largest for stimulus durations of 30 to 50 ms. An intravitreal injection of TTX essentially eliminated the focal macular PhNR. Conclusion. It is possible to record focal macular PhNRs from monkeys using a red stimulus spot on a blue background. Investigations of focal PhNRs can be a useful method to study inner retinal function of local areas in normal and diseased retinas.

Key Words: electroretinography, electrophysiology, ganglion cell