Heat stress and neural control of limb vasculature

热应激和肢体脉管系统的神经控制

• 批准号: 7113865
• 负责人: David M Keller
• 金额: $ 4.6万
• 依托单位: UT SOUTHWESTERN MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-04-01 至 2009-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7113865
• 关键词: adrenergic agents; alpha adrenergic receptor; baroreflex; blood pressure; body temperature regulation; cardiovascular pharmacology; clinical research; clonidine; heat stimulus; human subject; hyperthermia; laser Doppler flowmetry; leg; neuroregulation; norepinephrine; pathologic process; postdoctoral investigator; postural hypotension; sympathetic nervous system; tyramine; vasoconstriction

DESCRIPTION (provided by applicant): Fainting (i.e. orthostatic intolerance), or symptoms associated with fainting account for 3% of all emergency room visits and 6% of all hospital admissions. A combination of the heat stress with orthostasis leads to pronounced and consistent reductions in orthostatic tolerance during upright tilt, gravitational acceleration, and lower-body negative pressure. Despite clear evidence of marked reductions in orthostatic tolerance in hyperthermic individuals, the mechanisms responsible for the reduction in orthostatic tolerance in heat stressed individuals is incompletely understood. It has been suggested that increased muscle temperature may attenuate alpha-adrenergic vasoconstriction; however, the effect of heat on baroreflex-mediated vasoconstriction and specifically the alpha-adrenergic responsiveness in human limbs is incompletely understood. Although redistribution of cardiac output to the skin is likely to contribute in part to the reduction in orthostatic tolerance with whole-body heating, it remains unknown as to whether autonomic control (i.e. the baroreflex) of the vasculature supplying other organs such as skeletal muscle is reduced, further challenging the maintenance of arterial blood pressure during heat stress. Therefore, the goal of the projects outlined in this proposal is to test the hypothesis that increased temperature attenuates baroreflex-mediated vasoconstriction and that this event occurs through reduced alpha-adrenergic receptor responsiveness in human limbs.

描述（由申请人提供）：晕厥（即体位不耐受）或与晕厥相关的症状占所有急诊就诊的 3% 和所有入院的 6%。热应激与直立性的结合会导致直立倾斜、重力加速和下半身负压期间的直立性耐受性显着且一致地降低。尽管有明确的证据表明高温个体的直立耐受力显着降低，但导致热应激个体的直立耐受力降低的机制尚不完全清楚。有人提出，肌肉温度升高可能会减弱α-肾上腺素能血管收缩作用。然而，热对压力感受反射介导的血管收缩的影响，特别是对人体四肢α-肾上腺素能反应的影响尚不完全清楚。尽管心输出量到皮肤的重新分配可能部分导致全身加热的直立耐受性降低，但尚不清楚供应骨骼肌等其他器官的脉管系统的自主控制（即压力反射）是否会影响全身加热的直立耐受性。降低，进一步挑战热应激期间动脉血压的维持。因此，本提案中概述的项目的目标是检验这样的假设：温度升高会减弱压力反射介导的血管收缩，并且该事件是通过降低人体四肢中的α-肾上腺素受体反应性而发生的。