Effects of aging on the electroretinogram during ischemia-reperfusion in rats

The effects of aging on the electroretinogram (ERG) during ischemia-reperfusion were investigated in rats. Flash-elicited ERG (a-wave, b-wave, and oscillatory potentials (OPs)) was recorded in young (4 months old) and aged rats (over 18 months old) before, during, and after exposure to 30- or 120-min ischemia induced by increasing intraocular pressure to 80 mmHg. The choroidal blood flow, measured by means of laser Doppler flowmetry, decreased to 40 to 60% of the baseline value during ischemia. Young rats showed no significant difference in the amplitude of each ERG component during ischemia between 30- and 120-min ischemia groups; 78.0 +/- 4.9 vs. 76.1 +/- 3.6% for a-wave, 63.4 +/- 3.1 vs. 60.6 +/- 3.0% for b-wave, and 59.6 +/- 5.9 vs. 57.5 +/- 6.7% for SigmaOP. In aged rats, however, 120-min ischemia caused a greater decrease, to 56.7 +/- 3.1% of the baseline value, in the a-wave amplitude than 30-min ischemia did, to 70.8 +/- 3.2%. The reduction of each ERG component in both 30- and 120-min ischemia experiments was greater in aged rats than in young rats. The recovery time for the amplitude of each ERG component during reperfusion was longer in aged rats than in young rats. The latency of b-wave and the second component of OPs prolonged during ischemia, and recovery time for the latency was longer in aged rats than in young rats. These results suggest that the electrophysiological function of the retina is less tolerable against ischemia-reperfusion in aged rats than in young rats.