Gebber G L, Zhong S, Zhou S Y, Barman S M
Department of Pharmacology, Michigan State University, East Lansing 48824, USA.
Am J Physiol. 1997 Dec;273(6):R1932-45. doi: 10.1152/ajpregu.1997.273.6.R1932.
We used phase plane analysis to identify modes of frequency locking of the 10-Hz rhythm in sympathetic nerve discharge (SND) to the cardiac cycle in urethan-anesthetized, baroreceptor-innervated cats. Frequency locking occurred in rational ratios predicted by a generic mathematical construct called the Farey tree. Both simple harmonic ratios (e.g., 1:3) and complex ratios (e.g., 2:5) comprised of relatively prime integers (no common divisor) were identified under natural conditions. Frequency locking in such ratios is attributed to forcing of the 10-Hz oscillator by pulse-synchronous baroreceptor afferent nerve activity (BNA). Ventricular pacing changed the frequency of the 10-Hz rhythm as well as heart rate so as to maintain or change the ratio of frequency locking in a predictable way. Intriguingly, frequency locking of the 10-Hz rhythm to medullary raphe sympathoinhibitory stimuli in simple harmonic ratios was accompanied by increased power in the 10-Hz band of SND, whereas locking in complex ratios led to decreased 10-Hz power. These findings raise the possibility that pulse-synchronous BNA also exerts divergent actions on the 10-Hz rhythm depending on the ratio of frequency locking. Augmented 10-Hz power can be attributed to the resonant properties of oscillators that are periodically forced at the same phase in their cycle.
我们采用相平面分析方法，在乌拉坦麻醉、具有压力感受器传入神经支配的猫中，确定交感神经放电（SND）中10赫兹节律与心动周期的频率锁定模式。频率锁定以一种称为法雷树的通用数学结构所预测的有理数比出现。在自然条件下，既识别出了简单谐波比（如1:3），也识别出了由互质整数（无公约数）组成的复杂比（如2:5）。这种比率的频率锁定归因于脉冲同步压力感受器传入神经活动（BNA）对10赫兹振荡器的强迫作用。心室起搏改变了10赫兹节律的频率以及心率，从而以可预测的方式维持或改变频率锁定的比率。有趣的是，10赫兹节律以简单谐波比与延髓中缝交感抑制性刺激发生频率锁定时，SND的10赫兹频段功率增加，而以复杂比锁定则导致10赫兹功率降低。这些发现提出了一种可能性，即脉冲同步BNA也会根据频率锁定的比率对10赫兹节律产生不同的作用。增强的10赫兹功率可归因于振荡器的共振特性，这些振荡器在其周期的同一相位受到周期性强迫作用。
