Sinus arrhythmia is a normal respiration-related variation in heart rate that is diminished or absent in autonomic nerve dysfunction. The conventionally used measurements, R-R intervals and their standard deviations (RRSD), were made and compared with a computed statistic () in spontaneously diabetic BB rats and in age-matched nondiabetes-prone control rats. In addition, the effects of pentobarbital sodium anesthesia on RRSD and values in normal control rats were compared with those of nonanesthetized animals.

BB rats demonstrated a decrease in values after 8 wk of diabetes. This decrease became more marked with increased duration of diabetes. No differences in mean R-R intervals or RRSD were obtained between diabetic and nondiabetic rats until 24 wk of diabetes. Normal control rats showed a decrease in sinus arrythmia with age. Both RRSD and values were greatly decreased in anesthetized animals.

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