SYMPATHETIC NERVOUS SYSTEM INFLUENCE ON BLOOD PRESSURE REGULATION W/AGE

动脉血压（BP）对人体生理稳态具有重要影响，血压调节异常具有潜在的病理生理后果。自主神经系统（ANS）是BP心血管决定因素的关键调节因子。ANS对动脉血压的支持可能存在年龄相关的变化，这些变化可能至少部分与肾上腺素能受体敏感性的差异有关。本研究的总体目的是验证以下假设：1)基础ANS张力对健康成人静息血压及其循环决定因素的维持有重要贡献；2) ANS对BP的支持随着原发性（健康）衰老而增加；3)肾上腺素能受体敏感性随原发性衰老而降低。为了验证这些假设，我们使用自主神经节拮抗剂Trimethaphan来消除ANS对心血管组织的输入，从而量化其对维持血压的贡献。肾上腺素能激动剂苯肾上腺素（a-激动剂）和异丙肾上腺素（b-激动剂）在测量心率、血压和小腿血流时输注，以确定肾上腺素能受体的敏感性（即效应组织对肾上腺素能刺激的反应性）。正在研究两组健康受试者：27名年轻健康者（50%为女性）和27名年长健康者（50%为女性）。

Arterial blood pressure (BP) exerts a critical influence on physiological homeostasis in humans, and abnormalities in BP regulation have potential pathophysiological consequences. The autonomic nervous system (ANS) is a key regulator of the cardiovascular determinants of BP. There may be age-related changes in ANS support of arterial blood pressure, and these may be at least partially related to differences in adrenergic receptor sensitivity. The general aims of this study are to test the hypotheses that: 1) basal ANS tone makes a significant contribution to the maintenance of resting BP and its circulatory determinants in the healthy adult human; 2) ANS support of BP is increased with primary (healthy) aging; and 3) adrenergic receptor sensitivity is reduced with primary aging. To test these hypotheses we are using the autonomic ganglionic antagonist, Trimethaphan, to eliminate ANS input to cardiovascular tissues, and thereby quantify its contribution to the maintenance of BP. The adrenergic agonists phenylephrine (a-agonist), and isoproterenol (b-agonist) are infused during measurements of heart rate, BP, and calf blood flow, to determine adrenergic receptor sensitivity (i.e., effector tissue responsiveness to adrenergic stimuli). Two groups of healthy subjects are being studied: 27 young healthy (50% female), and 27 older healthy (50% female) adults.