We examined respiratory sinus arrhythmia (RSA) and possible interaction with respiratory frequency (f_R) and heart rate (HR) in spontaneously breathing, unanesthetized newborn Wistar rats (2- to 5-day-old; n = 54) and the adult rats (8-week-old; n = 34). Instantaneous heart rate (inst-HR) was calculated as the reciprocal of the inter-beat-interval. For each breath, RSA was determined as the difference between the maximum and minimum inst-HR value. The absolute RSA or RSA% (RSA per HR) were calculated as the average RSA of 10 consecutive breaths. RSA (or RSA%) in the newborn rats was significantly lower than that in the adult rats. Correlation coefficient between RSA (or RSA%) and 1/f_R or HR/f_R, but not HR, was significant in newborn rats, whereas only that between RSA (or RSA%) and HR was significant in adult rats. The power spectrum density of heartbeat fluctuation was detectable in both age groups. The present findings suggest that RSA exists and could be influenced by f_R, rather than HR, in newborn rats.

我们检查了自主呼吸、未麻醉的新生 Wistar 大鼠（2 至 5 日龄；n = 54）和成年大鼠的呼吸性窦性心律失常 (RSA) 以及与呼吸频率 ( f _R ) 和心率 (HR) 之间可能的相互作用。 （8 周龄；n = 34）。瞬时心率（inst -HR）计算为心跳间隔的倒数。对于每次呼吸，RSA 被确定为最大和最小瞬时心率值之间的差值。绝对 RSA 或 RSA%（RSA 每 HR）计算为 10 次连续呼吸的平均 RSA。新生大鼠的RSA（或RSA%）显着低于成年大鼠。在新生大鼠中，RSA（或RSA%）与1/ f _R或HR/ f _R之间的相关系数（而非HR）之间的相关系数显着，而在成年大鼠中，只有RSA（或RSA%）与HR 之间的相关系数显着。在两个年龄组中都可以检测到心跳波动的功率谱密度。目前的研究结果表明，新生大鼠中存在 RSA，并且可能受到f _R的影响，而不是 HR 的影响。