Hayashi T
Nihon Seirigaku Zasshi. 1981 Jun;43(6):171-81.
In 18 freely moving rabbits, R-R interval histograms, each of which included average value of 336,000 heart beats per day, were analyzed by means of long-term continuous recording of ECG. The mean heart rate of the day was 233 +/- 4 (SE) cpm and the coefficient of variation was 12.0 +/- 0.8 (SE)%. When the mean heart rate of the day increased, its coefficient of variation decreased proportionally (p less than 0.01). Not all the histograms resembled the normal distribution in contour as some of them apparently skewed to the side of tachycardia or bradycardia. The averaged heart rate of 18 rabbits showed such a circadian rhythm as it became tachycardia in the day while bradycardia at midnight. These results suggested the daily physiological rhythm in heart rates was controlled with the variation around the time varying mean heart rate, rather then by simple shortening or elongation of the cardiac cycles (i.e., "chronotrope").
在18只自由活动的兔子中，通过长期连续记录心电图，分析了R-R间期直方图，每个直方图包含每天336,000次心跳的平均值。当日平均心率为233±4（标准误）次/分钟，变异系数为12.0±0.8（标准误）%。当日平均心率增加时，其变异系数成比例下降（p<0.01）。并非所有直方图的轮廓都类似于正态分布，因为其中一些明显向心动过速或心动过缓一侧倾斜。18只兔子的平均心率呈现出昼夜节律，白天为心动过速，午夜为心动过缓。这些结果表明，心率的每日生理节律是由随时间变化的平均心率周围的变化控制的，而不是通过简单地缩短或延长心动周期（即“变时性”）来控制。
