Purpose. Cone electroretinograms (ERGs) can be recorded selectively by presenting flash stimuli against rod-desensitizing adapting field. Its amplitude changes in the course of light adaptation in flicker condition in human in the present study, the effects of luminance of the adapting field and that of fiasn stimuli on the amplitudes of the cone ERG were evaluated to isolate the physiological nature of the cone function in the rat. Methods. Cone ERGs were recorded in response to 2Hz or 20Hz flickers, with the luminance of either 0.86 or 1.30 log cd sec/m2, in normal 4-week-old albino SD rats. Each rat was kept in dark room at least for 12 hours, and then light adaptation was carried out by turning on the background field to variable luminance, ranging between -0.82 to 1.75 log cd/m2. ERGs were recorded repeatedly by in the course of light adaptation. After light adaptation, V-log-I function was recorded in each condition. Results. The amplitudes of ERGs were smaller in the early stage of light adaptation, and gradually increased in the course of adaptation reaching finally to plateau. Adapting field luminance did not modify the course of the amplitude increment. The ERG a-wave amplitudes to 2Hz stimulation and b-wave amplitude to 20Hz stimulation were increased at higher adapting field luminance. However, the b-wave amplitude to 2Hz stimulation decreased at higher luminance of the adapting field. Conclusions. The present results of the amplitude changes of ERGs during light adaptation in rats were similar to those in humans and mice, indicating the similar underlying mechanism involving the cone photoreceptor in the rat. Also this function is not different between 2Hz and 20hz stimuli. The different altitude of the b-wave amplitude to 2Hz stimulation, showing amplitude reduction at higher adapting luminance, suggests lnat the b-wave of ERG at 2Hz is not enhanced the pure cone function. Altough the a-wave amplitude at 2Hz is more enhanced the cone function, the amplitude is too small to compare in each condition. In conclusion, flicker stimulus seems to be optimal stimulation to isolate cone function in the rat.
|Investigative Ophthalmology and Visual Science
|Published - Feb 15 1996
All Science Journal Classification (ASJC) codes
- Sensory Systems
- Cellular and Molecular Neuroscience