Interstitial Norepinephrine and Heart Failure

描述（由申请方提供）：PI的长期目标是更好地了解正常受试者和心力衰竭（HF）患者运动期间调节自主神经反应的机制。 已知交感神经系统活动在正常受试者中随着运动而增加，并且在HF受试者中在休息时和响应于运动而增加。 外周交感神经活动增强和由此产生的去甲肾上腺素（NE）的神经血管水平增加引起血管收缩。 在本研究中，我们将用微透析法来测量去甲肾上腺素的组织间质浓度。 NE的间质浓度提供了神经血管连接处NE浓度的突出指数。 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标是检查运动肌肉中间质NE（NEi）和三磷酸腺苷（ATPi）升高的机制。 我们将检查增强的NEi是否是由于：1）交感神经的激活; 2）NE释放的ATP介导的增加;和/或3）NE的神经元再摄取（摄取1）的ATP介导的抑制。 我们的数据表明，ATPi在骨骼肌中的浓度上升，肌肉收缩。 我们假设ATP升高通过激活交感传出神经上的P2 X受体和/或通过抑制摄取1来增加NEi。 第三和第四个具体目标是研究为什么NEi和ATPi在充血性心力衰竭大鼠（心肌梗死模型）的骨骼肌中较高。 我们将检查HF大鼠中较高水平的NEi是否是由于：1）交感神经NE释放增加; 2）摄取1受损; 3）ATP升高抑制摄取1;或4）ATP激活交感神经末端P2 X受体。 第五个具体目标是确定间质NE和ATP是否在诱发HF的心肌梗死后随时间变化。 这些实验将检查ATP和NE在休息时，在肌肉收缩，并在肌肉拉伸。 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;和2）将特定物质递送到间隙空间。 我们的实验室在这些方法方面拥有丰富的专业知识。 据我们所知，像这样的实验从来没有在HF模型中进行过。 本提案中这些研究的完成将为重要心血管疾病运动期间的循环调节提供系统评价。

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.