Davy K P, Tanaka H, Andros E A, Gerber J G, Seals D R
Human Cardiovascular Research Laboratory, Center for Physical Activity, Disease Prevention, and Aging, Department of Kinesiology and Applied Physiology, University of Colorado at Boulder, Boulder, Colorado 80309, USA.
Am J Physiol. 1998 Nov;275(5):H1768-72. doi: 10.1152/ajpheart.1998.275.5.H1768.
Resting levels of muscle sympathetic nerve activity (MSNA) increase markedly with age in healthy adult humans. An age-related reduction in arterial baroreflex inhibition of MSNA could contribute to these elevations. To test this hypothesis, we measured MSNA using peroneal microneurography in young (age, 25 +/- 1 yr; n = 8) and older (69 +/- 1 yr; n = 7) healthy normotensive men before (baseline control) and during graded constant infusion of phenylephrine hydrochloride (0.5-2.0 microgram . kg-1. min-1) that produced a sustained approximately 10-mmHg increase in arterial blood pressure. Central venous pressure was controlled at baseline levels (+/-1 mmHg) using lower body negative pressure. Resting MSNA was approximately 95% higher in the older compared with the young subjects (43 +/- 5 vs. 22 +/- 3 bursts/min; P < 0.05). However, arterial baroreflex MSNA inhibitory responsiveness was similar in the older compared with the young subjects (254 +/- 112 vs. 259 +/- 40 arbitrary integration units/mmHg, respectively), although the percent reduction in MSNA was smaller in the older men (8.9 +/- 0.7 vs. 5.2 +/- 1.1%/mmHg), due to their elevated baseline levels. The reflex increase in the R-R interval was not different in the two groups (13 +/- 10 vs. 16 +/- 7 ms/mmHg). In summary, our findings suggest that arterial baroreflex inhibition of MSNA is preserved with age in healthy normotensive adult humans. As such, this mechanism does not appear to contribute to the age-related rise in tonic MSNA.
在健康成年人体内，静息状态下的肌肉交感神经活动（MSNA）水平会随着年龄的增长而显著升高。动脉压力反射对MSNA的抑制作用随年龄增长而减弱可能是导致这些升高的原因。为了验证这一假设，我们在年轻（年龄25±1岁；n = 8）和年长（69±1岁；n = 7）的健康血压正常男性中，使用腓骨微神经ography测量了MSNA，测量时间分别为基础状态（基线对照）以及在分级恒速输注盐酸去氧肾上腺素（0.5 - 2.0微克·kg-1·min-1）期间，该输注使动脉血压持续升高约10 mmHg。使用下体负压将中心静脉压控制在基线水平（±1 mmHg）。与年轻受试者相比，年长受试者的静息MSNA大约高95%（分别为43±5次/分钟和22±3次/分钟；P < 0.05）。然而，与年轻受试者相比，年长受试者的动脉压力反射MSNA抑制反应性相似（分别为254±112和259±40任意积分单位/mmHg），尽管由于年长男性的基线水平较高，他们的MSNA降低百分比较小（8.9±0.7%/mmHg对5.2±1.1%/mmHg）。两组的R - R间期反射性增加没有差异（13±10对16±7毫秒/mmHg）。总之，我们的研究结果表明，在健康血压正常的成年人体内，动脉压力反射对MSNA的抑制作用随年龄增长得以保留。因此，这一机制似乎并不是导致与年龄相关的紧张性MSNA升高的原因。
