[Age-related changes in the visual function of WBN/Kob rats--an electrophysiological study]

Changes in the visual function of the male WBN/Kob rat known as diabetic strain with increasing age were studied electrophysiologically. The measurements of electroretinogram (ERG) and visual evoked potential (VEP) in male WBN/Kob rats were performed at 5, 9, 13, 17, 23, 27, 36, 45, 54, 67 and 80 weeks of age, and compared with those in male Wistar/ST rats used as control. The prolonged latencies and decreased amplitudes of a- and b- waves and oscillatory potentials of ERG in WBN/Kob rats aged over 17 or 27 weeks were recorded under the light or after 20 min dark adaptation. The visual abnormality as indicated by non-recordable ERG was obvious in WBN/Kob rats aged 67 and 80 weeks. No changes of N1, P and N2 peak latencies of VEP were recorded in WBN/Kob rats with increasing age. The amplitudes between N1 peaks and P peaks decreased remarkably in WBN/Kob rats aged 54 weeks. The amplitudes of VEP in 67 or 80 weeks old rats in which ERG disappeared showed 26 or 28% of those in 5 weeks old rats. From these results, recording of ERG and VEP suggested that the visual abnormality occurred in male WBN/Kob rats aged 67 or 80 weeks and the process of visual abnormality with increasing age was clarified.