AGING AND ALPHA-ADRENERGIC CONTROL OF MUSCLE BLOOD FLOW

肌交感神经活动(MSNA)在运动过程中调节肢体血管张力、调节肢体血流量等方面起着重要作用。静息MSNA在人类中随着年龄的增长而显著增加，最近的研究表明，老年人对MSNA急性和慢性升高的血管收缩反应减弱。此外，缺乏关于老年人对收缩骨骼肌的交感神经控制血流的数据。拟议的实验将确定：1)随着年龄的增长，血管收缩迟钝是由于节后α-肾上腺素能受体反应性降低；2)特定的α-肾上腺素能受体亚型对基础和刺激血管张力的贡献随着年龄的变化而改变；以及3)与年轻人相比，老年人在活跃的骨骼肌中表现出更强烈的交感神经血管收缩。提出的实验设计的优点是，我们将针对特定的α受体亚型，在取消基础交感神经流出到前臂之前和之后，在星状神经节给予局部麻醉药。这些实验将为老年人休息和收缩骨骼肌的交感神经控制血流提供重要的新信息。

Muscle sympathetic nerve activity (MSNA) plays an important role in the regulation of basal limb vascular tone, as well as regulating limb blood flow during exercise. Resting MSNA increases markedly with age in humans, and recent studies suggest that the vasoconstrictor responses to acute and chronic elevations in MSNA are blunted in older adult humans. Additionally, data regarding sympathetic control of blood flow to contracting skeletal muscle in older adults is lacking. The proposed experiments will determine whether I) the blunted vasoconstriction with age is due to reduced postganglionic alpha-adrenergic receptor responsiveness; 2) the specific alpha-adrenergic receptor subtype contribution to basal and stimulated vascular tone is altered with age; and 3) older adults demonstrate more robust sympathetic vasoconstriction in active skeletal muscle compared with young adults. The strength of the proposed experimental design is that we will target the specific alpha- receptor subtypes before and after abolishing basal sympathetic outflow to the forearm with local anesthetics given at the stellate ganglion. These experiments will provide important new information about sympathetic control of blood flow to resting and contracting skeletal muscle in aging humans.