Interstitial Norepinephrine and Heart Failure

描述（由申请人提供）：PI的长期目标是更好地了解正常受试者和心力衰竭（HF）患者运动时自主神经反应的调节机制。众所周知，在正常受试者中，交感神经系统活动随着运动而增加，在心衰患者休息时和运动后交感神经系统活动增加。增强周围交感神经活动和由此增加的神经血管水平的去甲肾上腺素（NE）唤起血管收缩。在这个建议中，我们将用微透析方法测量NE的间质浓度。间质NE浓度是神经血管连接处NE浓度的重要指标。拟议的实验是基于我们实验室最近发表的研究以及过去一年收集的试点数据。第一个和第二个具体目的是研究运动肌肉中间质NE （NEi）和三磷酸腺苷（ATPi）升高的机制。我们将检查NEi增强是否由于：1)交感神经的激活；2) ATP介导的NE释放增加；和/或3)ATP介导的神经元对NE再摄取的抑制（摄取1）。我们的数据表明骨骼肌中的ATPi浓度随着肌肉收缩而升高。我们假设ATP升高通过激活交感传出神经上的P2X受体和/或抑制摄取来增加NEi。第三和第四个具体目的是研究为什么充血性心力衰竭（心肌梗死模型）大鼠骨骼肌中NEi和ATPi较高。我们将研究HF大鼠较高的NEi水平是否由于：1)交感神经释放的NEi增加；2)摄取障碍1；3) ATP升高对摄取1的抑制；或4)ATP激活交感神经末端P2X受体。第五个具体目的是确定心肌梗死诱发心衰后，间质NE和ATP是否随时间变化。这些实验将检测静止、肌肉收缩和肌肉拉伸时的ATP和NE。该提案的一个关键特征是微透析技术将用于：1)确定NEi和ATPi；2)将特定物质输送到间隙。我们的实验室在这些方法方面有丰富的专业知识。据我们所知，这样的实验从未在HF模型中进行过。本研究的完成将对运动期间循环调节在重要心血管疾病中的作用提供系统的评价。

DESCRIPTION (provided by applicant): The long-range goal of the PI is to better understand the mechanisms that regulate the autonomic responses during exercise in normal subjects and in patients with heart failure (HF). It is known that sympathetic nervous system activity is increased with exercise in normal subjects and is increased in HF subjects at rest and in response to exercise. Heightened peripheral sympathetic nerve activity and the resultant increased neurovascular levels of norepinephrine (NE) evoke vasoconstriction. In this proposal, we will measure interstitial concentrations of NE with the microdialysis method. Interstitial concentrations of NE provide an outstanding index of NE concentrations at the neurovascular junction. The proposed experiments are based on recently published studies from our laboratory as well as pilot data that have been gathered over the past year. The first and second specific aims are to examine the mechanisms for the rise in interstitial NE (NEi) and adenosine triphosphate (ATPi) in exercising muscle. We will examine if enhanced NEi is due to: 1) activation of the sympathetic nerves; 2) an ATP mediated increase in NE release; and/or 3) an ATP mediated inhibition of neuronal re-uptake of NE (uptake 1). Our data suggests that ATPi concentrations in skeletal muscle rise with muscle contraction. We hypothesize that elevated ATP increases NEi by activation of P2X receptors on the sympathetic efferent nerves, and/or by inhibition of uptake 1. The third and fourth specific aims are to examine why NEi and ATPi are higher in skeletal muscle of rats with congestive heart failure (myocardial infarctions model). We will examine if higher levels of NEi in HF rats are due to: 1) an increase in NE release by sympathetic nerve; 2) an impairment of uptake 1; 3) an inhibition of uptake 1 by elevated ATP; or 4) to activation of sympathetic nerve terminal P2X receptors by ATP. The fifth specific aim is to determine if interstitial NE and ATP change as a function of time after the myocardial infarct that induces HF. These experiments will examine ATP and NE at rest, during muscle contraction, and during muscle stretch. A key feature of this proposal is that microdialysis techniques will be used to: 1) determine NEi and ATPi; and 2) deliver specific substances to the interstitial space. Our laboratory has substantial expertise with these methods. To the best of our knowledge, experiments such as these have never been performed in a HF model. Completion of these studies in this proposal will provide a systematic evaluation of circulatory regulation during exercise in an important cardiovascular disease.