Department of Physiology, Graduate School of Health Sciences, Hiroshima University, Hiroshima 734-8551, Japan.
Auton Neurosci. 2010 Jun 24;155(1-2):59-67. doi: 10.1016/j.autneu.2010.01.007. Epub 2010 Feb 13.
Heart rate (HR) during exercise is controlled by cardiac sympathetic (CSNA) and vagal (CVNA) efferent nerve activity and plasma catecholamines. To determine their relative contribution to the exercise tachycardia, we examined the effects of adrenalectomy (ADX) and autonomic blockades on the HR response during treadmill exercise for 32min in 13 conscious rats. The baseline HR was not influenced by ADX, suggesting no significant role of adrenal catecholamines on the baseline HR. Since the baseline HR was increased 61beats/min by atropine methyl nitrate (1.5mg/kg) and decreased 26beats/min by atenolol (3mg/kg), CVNA determined the baseline HR more than CSNA. ADX did not affect the immediate increase in HR at 0-12s from the exercise onset but reduced the subsequent increase in HR at 13-30s. These increases in HR at the early period of exercise were more blunted by atenolol than atropine. On the other hand, the peak tachycardia response of 99+/-8beats/min at the end of exercise, which was the same between the intact and ADX conditions, was blunted to 73% by atenolol, to 77% by atropine, and to 35% by combined atenolol and atropine, respectively. In conclusion, it is likely that the tachycardia at the beginning of dynamic exercise is predominantly determined by the cardiac autonomic nerve activity, especially by a prompt increase in CSNA, and that the hormonal mechanism due to adrenal epinephrine contributes to a further increase in HR approximately in 13s from the onset of exercise.
心率（HR）在运动中受心脏交感神经（CSNA）和迷走神经（CVNA）传出神经活动和血浆儿茶酚胺的控制。为了确定它们对运动性心动过速的相对贡献，我们检查了肾上腺切除术（ADX）和自主神经阻滞对 13 只清醒大鼠进行 32 分钟跑步机运动时 HR 反应的影响。基础 HR 不受 ADX 影响，提示肾上腺儿茶酚胺对基础 HR 没有重要作用。由于基线 HR 被硝酸甲硫基肾上腺素（1.5mg/kg）增加了 61 次/分钟，被阿替洛尔（3mg/kg）降低了 26 次/分钟，因此 CVNA 决定了基线 HR 比 CSNA 更重要。ADX 对运动开始后 0-12s 时 HR 的即刻增加没有影响，但减少了随后 13-30s 时 HR 的增加。在运动早期，阿替洛尔对 HR 增加的抑制作用大于阿托品。另一方面，运动结束时的峰值心动过速反应为 99+/-8 次/分钟，在完整和 ADX 条件下相同，被阿替洛尔抑制到 73%，被阿托品抑制到 77%，被阿替洛尔和阿托品联合抑制到 35%。总之，运动开始时的心动过速可能主要由心脏自主神经活动决定，特别是由 CSNA 的迅速增加决定，而肾上腺肾上腺素引起的激素机制大约在运动开始后 13s 对 HR 的进一步增加有贡献。
