Federici A, Sorrentino G, Di Benedetta C
Boll Soc Ital Biol Sper. 1983 Jan 31;59(1):8-13.
The time-dependency of vagal effects on P-P cycle was studied in rabbits, chosen because of high heart rate, in order to verify the occurrence of this phenomenon already described for animals with lower heart rate. In five rabbits with different resting cardiac cycles, vagal stimuli were delivered randomly. The results indicate that for heart rates higher than 120 beats/min no occurrence of Brown and Eccles' time-dependency was observed. It is evident, however, the different responsiveness of the pacemaker to vagal stimuli delivered at different times of the cardiac cycle. In particular a stimulus given beyond 40-50% of the cardiac cycle does not affect the same but the next cycle.
为了验证在心率较低的动物中已经描述过的这种现象是否会发生，我们选用了心率较高的兔子来研究迷走神经对P-P周期的时间依赖性。在五只静息心动周期不同的兔子中，随机施加迷走神经刺激。结果表明，对于心率高于120次/分钟的情况，未观察到布朗和埃克尔斯所描述的时间依赖性。然而，很明显，起搏器对在心动周期不同时间施加的迷走神经刺激具有不同的反应性。特别是在心动周期超过40%-50%时给予的刺激不会影响同一周期，而是会影响下一个周期。
