Human Informatics and Interaction Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan.
Department of Integrative Physiology, Graduate School of Biomedical and Health Sciences, Hiroshima University, Minami-ku, Hiroshima, Japan.
Exp Physiol. 2023 Jan;108(1):28-37. doi: 10.1113/EP090718. Epub 2022 Nov 20.
What is the central question of this study? Standing up can cause hypotension and tachycardia. Accumulated evidence poses the simple question, does the cardiac baroreflex operate at the onset of standing up? If the cardiac baroreflex is suppressed, what mechanism is responsible for baroreflex inhibition? What is the main finding and its importance? In cats, we found blunting of cardiac baroreflex sensitivity in the pressor range at the onset of voluntary hindlimb standing, but not of passive hindlimb standing. This finding suggests that central command suppresses pressor-evoked bradycardia at the onset of standing up, probably in advance, to prevent or buffer orthostatic hypotension.
It remains unclear whether cardiac baroreflex function is preserved or suppressed at the onset of standing up. To answer the question and, if cardiac baroreflex is suppressed, to investigate the mechanism responsible for the suppression, we compared the sensitivity of the arterial cardiac baroreflex at the onset of voluntary and passive hindlimb standing in conscious cats. Cardiac baroreflex sensitivity was estimated from the maximal slope of the baroreflex curve between the responses of systolic arterial blood pressure and heart rate to a brief occlusion of the abdominal aorta. The systolic arterial blood pressure response to standing up without aortic occlusion was greater in the voluntary case than in the passive case. Cardiac baroreflex sensitivity was clearly decreased at the onset of voluntary standing up compared with rest (P = 0.005) and the onset of passive standing up (P = 0.007). The cardiac baroreflex sensitivity at the onset of passive standing up was similar to that at rest (P = 0.909). The findings suggest that central command would transmit a modulatory signal to the cardiac baroreflex system during the voluntary initiation of standing up. Furthermore, the present data tempt speculation on a close relationship between central inhibition of the cardiac baroreflex and the centrally induced tachycardiac response to standing up.
本研究的核心问题是什么？站立会导致低血压和心动过速。越来越多的证据提出了一个简单的问题，即心脏压力反射在站立开始时起作用吗？如果心脏压力反射受到抑制，是什么机制导致了压力反射抑制？主要发现及其重要性是什么？在猫中，我们发现，在自愿后腿站立的起始阶段，压力反射敏感性在升压范围内减弱，但在后腿被动站立时则没有减弱。这一发现表明，中枢指令在站立开始时抑制了压力诱发的心动过缓，可能是提前抑制，以防止或缓冲直立性低血压。
目前尚不清楚心脏压力反射功能在站立开始时是保持还是受到抑制。为了回答这个问题，如果心脏压力反射受到抑制，那么研究导致抑制的机制，我们比较了在清醒猫中自愿和被动后腿站立开始时动脉心脏压力反射的敏感性。心脏压力反射敏感性是通过主动脉腹部短暂闭塞时收缩压和心率反应的压力反射曲线的最大斜率来估计的。在没有主动脉闭塞的情况下，站立开始时的收缩压反应在自愿情况下大于被动情况下。与休息时相比（P=0.005）和被动站立开始时相比（P=0.007），自愿站立开始时的心脏压力反射敏感性明显降低。被动站立开始时的心脏压力反射敏感性与休息时相似（P=0.909）。这些发现表明，在自愿站立开始时，中枢命令会向心脏压力反射系统传递一个调节信号。此外，目前的数据推测，心脏压力反射的中枢抑制与站立引起的心动过速反应之间存在密切关系。
Zotero 插件
