Interstitial Norepinephrine and Heart Failure

描述(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)患者在运动过程中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的进行而增加，而在心力衰竭受试者中，在安静时和对运动的反应中，交感神经系统的活动也会增加。周围交感神经活动增强和由此导致的神经血管去甲肾上腺素(NE)水平增加引起血管收缩。在这个方案中，我们将用微透析法测量组织间去甲肾上腺素浓度。NE间质浓度是神经血管交界处NE浓度的一个显著指标。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。第一个和第二个特定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。我们将研究增强的NEI是否源于：1)交感神经的激活；2)ATP介导的NE释放的增加；和/或3)ATP介导的神经元对NE的再摄取的抑制(摄取1)。我们的数据表明，骨骼肌中ATPI的浓度随着肌肉收缩而上升。我们假设，升高的ATP通过激活交感传出神经上的P2X受体和/或通过抑制摄取1来增加NEI。第三和第四个特定目的是研究充血性心力衰竭(心肌梗死模型)大鼠骨骼肌中NEI和ATPI升高的原因。我们将研究心衰大鼠的NEI水平升高是否归因于：1)交感神经释放NE增加；2)摄取受损；3)ATP升高抑制摄取1；或4)ATP激活交感神经末梢P2X受体。第五个具体目的是确定心肌梗死后是否间质NE和ATP随时间的变化而导致心力衰竭。这些实验将在休息、肌肉收缩和肌肉拉伸时检测ATP和NE。这项提议的一个主要特点是，微透析技术将被用于：1)测定NEI和ATPI；以及2)将特定物质输送到间隙。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，这样的实验从未在高频模型中进行过。这项建议中的这些研究的完成将为一种重要的心血管疾病在运动期间的循环调节提供系统的评估。

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.