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) 患者运动期间调节自主反应的机制。 众所周知，正常受试者的交感神经系统活性随着运动而增加，而心力衰竭受试者在休息时和对运动的反应中交感神经系统活性也增加。 周围交感神经活动增强，从而导致去甲肾上腺素 (NE) 的神经血管水平增加，引起血管收缩。 在本提案中，我们将使用微透析方法测量 NE 的间质浓度。 NE 的间质浓度提供了神经血管连接处 NE 浓度的重要指标。 拟议的实验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 NEi 增强是否是由于：1）交感神经激活； 2) ATP介导的NE释放增加；和/或 3) ATP 介导的神经元再摄取 NE 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，升高的 ATP 通过激活交感传出神经上的 P2X 受体和/或抑制摄取 1 来增加 NEi。第三和第四个具体目标是检查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。 我们将检查 HF 大鼠中 NEi 水平较高是否是由于：1）交感神经释放的 NE 增加； 2) 吸收障碍1； 3) 通过升高的 ATP 抑制摄取 1；或4)通过ATP激活交感神经末梢P2X受体。 第五个具体目标是确定诱发心力衰竭的心肌梗死后间质 NE 和 ATP 是否随时间变化。 这些实验将检查静止时、肌肉收缩期间和肌肉拉伸期间的 ATP 和 NE。 该提案的一个关键特点是微透析技术将用于： 1) 确定 NEi 和 ATPi； 2) 将特定物质输送至间隙空间。 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，此类实验从未在 HF 模型中进行过。 完成本提案中的这些研究将为重要心血管疾病运动过程中的循环调节提供系统评估。

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.