Human Informatics and Interaction Research Institute, National Institute of Advanced Industrial Science and Technology, Ibaraki, Japan.
Department of Integrative Physiology, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan.
Physiol Rep. 2022 Jun;10(12):e15371. doi: 10.14814/phy2.15371.
It remains undetermined whether the cardiac component of the entire arterial baroreflex is blunted even at the onset of low-intensity exercise. We sought to examine the moment-to-moment sensitivity of the cardiac baroreflex during walking at different speeds and the presumed mechanisms responsible for baroreflex modulation in conscious cats. Arterial baroreflex sensitivity for heart rate was estimated from the baroreflex ratio between changes in systolic arterial blood pressure and heart rate and from the slope of the baroreflex curve between the cardiovascular responses to brief occlusion of the abdominal aorta. Treadmill walking was performed for 1 min at three levels of speed (low: 20-30 m/min, moderate: 40 m/min, and high: 50-60 m/min) or for 3 min at the stepwise change of speed (low to high to low transition). Cardiac baroreflex sensitivity was blunted at the onset of walking, irrespective of speed. Thereafter, the blunted cardiac baroreflex sensitivity was restored around 15 s of walking at any speed, while the blunting occurred again at 45 s of high-speed walking. The inhibition of cardiac baroreflex sensitivity also occurred (1) during the speed transition from low to high and (2) at 45 s of high-speed exercise of the stepwise exercise. The blunted cardiac baroreflex sensitivity was restored immediately to the resting level during the speed transition from high to low, despite sustained pressor and tachycardiac responses. Therefore, moment-to-moment modulation of the cardiac baroreflex during exercise would occur in association with motor intention (i.e., exercise onset) and effort (i.e., treadmill speed).
即使在低强度运动开始时，整个动脉压力反射的心脏成分是否仍然迟钝仍不确定。我们试图检查在不同速度下行走时心脏压力反射的瞬间敏感性，以及在有意识的猫中负责压力反射调节的假定机制。心率的动脉压力反射敏感性是通过收缩压和心率变化之间的压力反射比以及心血管对腹主动脉短暂闭塞的反应之间的压力反射曲线的斜率来估计的。在三种速度水平（低：20-30 m/min、中：40 m/min 和高：50-60 m/min）下进行了 1 分钟的跑步机行走，或者在速度逐步变化（低到高到低过渡）下进行了 3 分钟的行走。无论速度如何，在开始行走时心脏压力反射敏感性都会降低。此后，在任何速度下行走 15 秒左右，迟钝的心脏压力反射敏感性得到恢复，而在高速行走 45 秒时再次发生迟钝。在从低到高的速度过渡期间（1）和在逐步运动的 45 秒高速运动期间（2）也会发生心脏压力反射敏感性抑制。尽管血压升高和心动过速持续存在，但在从高到低的速度过渡期间，心脏压力反射敏感性的迟钝会立即恢复到静息水平。因此，运动过程中心脏压力反射的瞬间调节会与运动意图（即运动开始）和努力（即跑步机速度）相关。
