Miki Kenju, Ikegame Shizuka, Yoshimoto Misa
Autonomic Physiology Laboratory, Faculty of Life Science and Human Technology, Nara Women's University, Kita-Uoya Nishimachi, Nara, Japan.
Front Physiol. 2022 Apr 4;13:858654. doi: 10.3389/fphys.2022.858654. eCollection 2022.
In this review, by evaluating the responses during freezing, rapid eye movement (REM) sleep, and treadmill exercise, we discuss how multiple baroreflex loops arranged in parallel act on different organs to modulate sympathetic nerve activity (SNA) in a region-specific and coordinated manner throughout the body. During freezing behaviors, arterial pressure (AP) remains unchanged, heart rate (HR) persistently decreases, renal SNA (RSNA) increases, and lumbar SNA (LSNA) remains unchanged. The baroreflex curve for RSNA shifts upward; that for LSNA remains unchanged; and that for HR shifts to the left. These region-specific changes in baroreflex curves are responsible for the region-specific changes in RSNA, LSNA, and HR during freezing. The decreased HR could allow the heart to conserve energy, which is offset by the increased RSNA caused by decreased vascular conductance, resulting in an unchanged AP. In contrast, the unchanged LSNA leaves the muscles in readiness for fight or flight. During REM sleep, AP increases, RSNA and HR decrease, while LSNA is elevated. The baroreflex curve for RSNA during REM sleep is vertically compressed in comparison with that during non-REM sleep. Cerebral blood flow is elevated while cardiac output is decreased during REM sleep. To address this situation, the brain activates the LSNA selectively, causing muscle vasoconstriction, which overcomes vasodilation of the kidneys as a result of the decreased RSNA and cardiac output. Accordingly, AP can be maintained during REM sleep. During treadmill exercise, AP, HR, and RSNA increase simultaneously. The baroreflex curve for RSNA shifts right-upward with the increased feedback gain, allowing maintenance of a stable AP with significant fluctuations in the vascular conductance of working muscles. Thus, the central nervous system may employ behavior-specific scenarios for modulating baroreflex loops for differential control of SNA, changing the SNA in a region-specific and coordinated manner, and then optimizing circulatory regulation corresponding to different behaviors.
在本综述中，通过评估在僵住、快速眼动（REM）睡眠和跑步机运动期间的反应，我们讨论了多个并行排列的压力反射环路如何作用于不同器官，以在全身以区域特异性和协调性的方式调节交感神经活动（SNA）。在僵住行为期间，动脉压（AP）保持不变，心率（HR）持续下降，肾交感神经活动（RSNA）增加，而腰交感神经活动（LSNA）保持不变。RSNA的压力反射曲线向上移动；LSNA的压力反射曲线保持不变；HR的压力反射曲线向左移动。压力反射曲线的这些区域特异性变化导致了僵住期间RSNA、LSNA和HR的区域特异性变化。HR降低可使心脏保存能量，这被血管传导性降低引起的RSNA增加所抵消，从而导致AP不变。相比之下，LSNA不变使肌肉随时准备好战斗或逃跑。在REM睡眠期间，AP升高，RSNA和HR降低，而LSNA升高。与非REM睡眠期间相比，REM睡眠期间RSNA的压力反射曲线垂直压缩。REM睡眠期间脑血流量升高而心输出量降低。为应对这种情况，大脑选择性地激活LSNA，导致肌肉血管收缩，这克服了由于RSNA和心输出量降低导致的肾脏血管舒张。因此，在REM睡眠期间可以维持AP。在跑步机运动期间，AP、HR和RSNA同时增加。随着反馈增益增加，RSNA的压力反射曲线向右上方移动，从而在工作肌肉血管传导性显著波动的情况下维持稳定的AP。因此，中枢神经系统可能采用特定于行为的方案来调节压力反射环路，以对SNA进行差异控制，以区域特异性和协调性的方式改变SNA，然后优化与不同行为相对应的循环调节。
