Fisher James P, Ogoh Shigehiko, Ahmed Abrar, Aro Michael R, Gute Dean, Fadel Paul J
Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO 65212, USA.
Am J Physiol Heart Circ Physiol. 2007 Jul;293(1):H777-83. doi: 10.1152/ajpheart.00199.2007. Epub 2007 Apr 20.
We investigated the influence of aging on cardiac baroreflex function during dynamic exercise in seven young (22 +/- 1 yr) and eight older middle-aged (59 +/- 2 yr) healthy subjects. Carotid-cardiac baroreflex function was assessed at rest and during moderate-intensity steady-state cycling performed at 50% heart rate reserve (HRR). Five-second pulses of neck pressure and neck suction from +40 to -80 Torr were applied to determine the operating point gain (G(OP)) and maximal gain (G(MAX)) of the full carotid-cardiac baroreflex function curve and examine baroreflex resetting during exercise. At rest, mean arterial pressure (MAP) and heart rate were similar between the younger and older subjects. In contrast, the resting G(OP) and G(MAX) were significantly lower in the older subjects. The increase in MAP from rest to exercise was greater in the older subjects (Delta +20 +/- 2 older vs. Delta +6 +/- 3 younger mmHg; P < 0.001). However, the G(OP) was similar in both groups during exercise because of a reduction in the younger subjects. In contrast, G(MAX) was unchanged from rest and therefore remained lower in older subjects (-0.19 +/- 0.05 older vs. -0.42 +/- 0.05 younger beats.min(-1).mmHg(-1); 50% HRR; P < 0.001). Furthermore, exercise resulted in an upward and rightward resetting of the cardiac baroreflex function curve in both groups. Collectively, these findings suggest that the cardiac baroreflex function curve appropriately resets during exercise in older subjects but operates at a reduced G(MAX) primarily because of age-related reductions in carotid-cardiac control manifest at rest.
我们研究了衰老对7名年轻（22±1岁）和8名老年中年（59±2岁）健康受试者动态运动期间心脏压力反射功能的影响。在静息状态以及以心率储备（HRR）的50%进行中等强度稳态骑行期间，评估颈动脉-心脏压力反射功能。施加从+40至-80托的5秒颈部压力和颈部抽吸脉冲，以确定完整颈动脉-心脏压力反射功能曲线的工作点增益（G(OP)）和最大增益（G(MAX)），并检查运动期间的压力反射重调定。静息时，年轻和老年受试者的平均动脉压（MAP）和心率相似。相比之下，老年受试者静息时的G(OP)和G(MAX)显著更低。老年受试者从静息到运动时MAP的升高幅度更大（老年受试者Δ+20±2 mmHg，年轻受试者Δ+6±3 mmHg；P<0.001）。然而，由于年轻受试者的降低，两组运动期间的G(OP)相似。相比之下，G(MAX)从静息时无变化，因此老年受试者中仍较低（老年受试者-0.19±0.05次·分钟-1·mmHg-1，年轻受试者-0.42±0.05次·分钟-1·mmHg-1；50% HRR；P<0.001）。此外，运动导致两组心脏压力反射功能曲线向上和向右重调定。总体而言，这些发现表明，老年受试者运动期间心脏压力反射功能曲线可适当重调定，但主要由于静息时颈动脉-心脏控制的年龄相关降低，其以降低的G(MAX)运行。
