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（即正常不宽容），或与晕厥相关的症状，占所有急诊室就诊的3％，占所有住院的6％。在直立倾斜，重力加速度和下半身负压期间，热应力与正交性的结合导致体位耐受性的明显且一致。尽管明显的证据表明，高温个体的体位耐受性显着降低，但尚不完全了解导致热压力个体处体耐受性降低的机制。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。但是，尚不完全了解热量对压力反射介导的血管收缩，特别是人体四肢中α-肾上腺素能反应的影响。尽管将心输出量重新分布为皮肤，可能会导致降低到体制加热的体位耐受性，但尚不清楚自主控制（即脉管体）是否供应其他器官（例如骨骼肌）（例如骨骼肌）的脉管肌肉，进一步降低了骨骼肌肉，进一步挑战热应力的维持，挑战热压力的维持。因此，该提案中概述的项目的目的是检验以下假设，即升高温度减弱了压力反射介导的血管收缩，并且该事件是通过降低人类四肢中α-肾上腺素能受体的反应而发生的。