AUTONOMIC MODULATION OF RESTING AND EXERCISE CARDIAC PERFORMANCE

随着年龄的增长，自主神经系统发生了深刻的变化。 活动，无论是在休息和运动，以及减少在 对自主神经刺激的心血管反应。 我们已经进行了三次 独立但概念上相互关联的研究，以量化 老化和心血管功能的自主调节之间的联系。 A. 传出肌肉交感神经活动（MSNA）记录从 腓神经将在巴尔的摩纵向研究中进行， 老年人（BLSA）男性和女性在休息和响应时的广泛年龄范围 压力反射刺激和静态锻炼。 我们假设， 除了年龄，其他因素，如性别，有氧健身和身体 组合物将调节MSNA对这些刺激的反应。 B。 到 确定β-肾上腺素能系统对年龄相关性 在有氧运动（EX）过程中的血流动力学变化，我们进行了最大的 25名年龄28-72岁的健康男性在急性β- 静脉注射普萘洛尔阻断。 在这些人中，舒张末期容积 峰值负荷时的EDVI随年龄增长而下降（r=-0.45）， 与每搏输出量指数（SVI）相关的下降（r= 0.48，p<0.05） 有70个未被屏蔽的人。心率（HR）随着年龄的增长而下降， 与对照组相比，普萘洛尔治疗组的男性心率减慢（0.46次/分/年 (1.09次/分/年）。 在这个时代， 普萘洛尔后的回归是EDVI和SVI的大幅增加， 年轻男性的HR大幅下降。 同样，静脉注射普萘洛尔 导致年轻人（27 q8 yr）的EX峰值充盈率降低，但 老年人（62 q 6 yr）男性相对于他们的未服药年龄的同龄人。 我们的结论 β-肾上腺素能反应的年龄差异是许多 年龄相关的血液动力学变化，在激烈的有氧EX。 C. 到 确定自主神经系统在年龄相关性 有氧能力和血浆儿茶酚胺的差异，我们进行了 静脉注射普萘洛尔（0.15 mg/kg）进行急性自主神经阻滞， 阿托品（0.025 mg/kg），10例青年（<40岁）和10例老年（>60岁） 健康的BLSA志愿者在最大跑步机运动之前，在安慰剂中， 对照交叉试验。 之前监测血浆儿茶酚胺， 在运动期间和运动后立即进行。 统计分析将 确定年龄本身是否差异性地改变了 阻断VO 2 max、HR和血压反应及血浆儿茶酚胺 在最大限度的运动。

Advancing age is accompanied by profound changes in autonomic nervous syste activity, both at rest and during exercise as well as reduction in the cardiovascular response to autonomic stimulation. We have undertaken three separate but conceptually interrelated studies to quantify the relationship between aging and autonomic modulation of cardiovascular performance. A. Efferent muscle sympathetic nerve activity (MSNA) recording from the peroneal nerve will be performed in the Baltimore Longitudinal Study of Aging (BLSA) men and women across a broad age range at rest and in response to baroreflex stimulation and static exercise. We hypothesize that in addition to age, other factors such as gender, aerobic fitness and body composition will modulate the MSNA response to these stimuli. B. To ascertain the importance of the beta-adrenergic system on age-associated changes in hemodynamics during aerobic exercise (EX), we performed maximal cycle EX in 25 healthy men ages 28-72 yr from the BLSA after acute beta- blockade with intravenous propranolol. In these men,end-diastolic volume index (EDVI) at peak workload declined with age (r= - 0.45) causing an age- associated decline in stroke volume index (SVI) (r= 0.48, p<0.05) not present in 70 unblocked men. The decline in heart rate (HR) with age in propranolol-treated men was blunted (0.46 beats/min/yr) compared to control (1.09 beats/min/yr). The primary reason for the slope shifts in the age regressions after propranolol was a large increase in EDVI and SVI and a large decrease in HR in younger men. Similarly, intravenous propranolol resulted in reduced peak filling rates with EX in young (27 q 8 yr) but not older (62 q 6 yr) men relative to their unmedicated age peers. We conclude that age differences in beta-adrenergic responsiveness underlie many of the age-associated changes in hemodynamics during vigorous aerobic EX. C. To determine the role of the autonomic nervous system on age-associated differences in aerobic capacity and plasma catecholamines, we performed acute autonomic blockade with intravenous propranolol (0.15 mg/kg) and atropine (0.025 mg/kg) in 10 young (<40 yr old) and 10 older (>60 yr old) healthy BLSA volunteers prior to maximal treadmill exercise, in a placebo- controlled crossover trial. Plasma catecholamines were monitored before, during and immediately following exercise. Statistical analysis will determine whether age per se differentially modifies the effect of autonomi blockade on VO2max, HR and blood pressure response and plasma catecholamine during maximal exercise.