Gadolinium does not blunt the cardiovascular responses at the onset of voluntary static exercise in cats: a predominant role of central command
Gadolinium does not blunt the cardiovascular responses at the onset of voluntary static exercise in cats: a predominant role of central command
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DOI：
10.1152/ajpheart.00028.2006
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发表时间：
2007-01-01
影响因子：
4.8
通讯作者：
Inomoto, Atsushi
中科院分区：
文献类型：
--
作者：
Matsukawa, Kanji;Nakamoto, Tomoko;Inomoto, Atsushi
自主静态运动开始时的心血管适应性是由自主神经系统控制的。心血管适应的神经机制有两种：一种是来自大脑高级中枢的中枢指令，另一种是来自收缩肌肉中机械感受器激活的肌肉机械敏感反射。为了研究在静态运动中产生初始心血管适应的主要机制，我们研究了静脉注射钆（55 μ mol/kg）对有意识猫在自愿静态运动（用前肢按压杆）开始时心率（HR）和平均动脉血压（MAP）增加的影响。钆是一种拉伸激活离子通道阻断剂。在自愿静态运动开始时，心率增加31 +/- 5次/分，MAP增加15 +/- 1 mmHg。钆既不影响基线值，也不影响运动开始时HR和MAP的初始增加，尽管施加在杆上的峰值力倾向于降低到钆前控制值的65%。此外，我们研究了钆对麻醉猫前肢或后肢被动机械拉伸时HR和MAP反射反应的影响（分别为18 +/- 7次/分钟和30 +/- 6 mmHg）。钆显著减弱了被动拉伸引起的HR和MAP的增加，表明钆阻断了拉伸激活的离子通道，从而减弱了被动机械肢体拉伸时的反射性心血管反应。我们得出的结论是，在自愿静态运动开始时，最初的心血管适应主要是由来自高级脑中心的中央指令的前馈控制引起的，而不是由肌肉机械反射引起的。
The cardiovascular adaptation at the onset of voluntary static exercise is controlled by the autonomic nervous system. Two neural mechanisms are responsible for the cardiovascular adaptation: one is central command descending from higher brain centers, and the other is a muscle mechanosensitive reflex from activation of mechanoreceptors in the contracting muscles. To examine which mechanism played a major role in producing the initial cardiovascular adaptation during static exercise, we studied the effect of intravenous administration of gadolinium (55 mu mol/kg), a blocker of stretch-activated ion channels, on the increases in heart rate (HR) and mean arterial blood pressure (MAP) at the onset of voluntary static exercise (pressing a bar with a forelimb) in conscious cats. HR increased by 31 +/- 5 beats/min and MAP increased by 15 +/- 1 mmHg at the onset of voluntary static exercise. Gadolinium affected neither the baseline values nor the initial increases of HR and MAP at the onset of exercise, although the peak force applied to the bar tended to decrease to 65% of the control value before gadolinium. Furthermore, we examined the effect of gadolinium on the reflex responses in HR and MAP (18 +/- 7 beats/min and 30 +/- 6 mmHg, respectively) during passive mechanical stretch of a forelimb or hindlimb in anesthetized cats. Gadolinium significantly blunted the passive stretch-induced increases in HR and MAP, suggesting that gadolinium blocks the stretch-activated ion channels and thereby attenuates the reflex cardiovascular responses to passive mechanical stretch of a limb. We conclude that the initial cardiovascular adaptation at the onset of voluntary static exercise is predominantly induced by feed-forward control of central command descending from higher brain centers but not by a muscle mechanoreflex.