Investigation on diabetic autonomic neuropathy assessed by power spectral analysis of heart rate variability in WBN/Kob rats

This article investigates the development of cardiovascular;auto nomic dysf unction caused by diabetes mellitus. We performed power spectral analysis o f heart rate variability in WBN/Kob rats as a model of spontaneous diabetes . The heart rate of the rats was measured continuously for 24 hours with an implanted telemetric transmitter, and power spectral analysis of heart rat e variability was performed on continuous electrocardiograms. At 4 to 5 mon ths of age, the rats indicated a tendency toward a decrease in plasma insul in concentration without hyperglycemia. At 8 to 9 months of age, they showe d remarkable hyperglycemia, loss of the circadian rhythm of the heart rate, and reversion or loss of the circadian rhythm of the blood pressure. By th e power spectral analysis of heart rate variability, it became apparent tha t the circadian rhythm of the low frequency/high frequency ratio was absent even in prediabetic WBN/Kob rats. In addition, the circadian rhythms of th e high-frequency power level and low frequency/high frequency ratio were ab sent in diabetic WBN/Kob rats. These findings indicate that the autonomic n ervous system in WBN/Kob rats is progressively damaged from the prediabetic to diabetic state. In conclusion, diabetic autonomic neuropathy may be cha racterized by the appearance of sympathetic overactivity that precedes the impairment of parasympathetic activity.