Remodeling of the guinea pig intrinsic cardiac plexus with chronic heart disease

描述(申请人提供)：以前的研究表明，自主神经传出神经张力的失衡，副交感神经活动减少，加上交感神经流出增加和异质性，增加了心律失常和猝死的风险。虽然心脏病的进展影响心脏控制的多个方面，但正是外周自主神经处理及其投射的变化最终决定了心脏的神经元协调。心脏固有神经系统(ICN)是这种神经控制的最终共同途径，它整合了来自多个输入的信息，并介导了对局部心脏指数的短环反射控制。虽然许多研究都集中在心脏应激引起的神经节后对心脏的神经支配模式的改变，但很少有人关注自主神经节内信息处理的关键作用以及它们如何重塑/适应施加的应激。我们的假设是，心脏应激诱导的ICN内的适应促进了传出副交感神经输出的协调，这些变化反映在选定的心脏固有神经元群体的功能和表型变化中。ICN内的这些心脏保护性适应可以部分抵消过度交感神经兴奋与心脏应激相关的适应不良效应。大量研究已经确定了与心脏重构相关的分子机制，包括肾素-血管紧张素系统活性增加，一氧化氮(NO)产生的变化，以及终末器官对神经递质的敏感性改变。对于这些因素中的每一种，虽然它们对心肌细胞功能的直接影响是众所周知的，但最近的数据表明，它们的许多心脏效应是通过心脏神经系统内功能的改变来调节的。为了具体解决这些问题，这项提案将使用两种不同的心脏病动物模型来评估ICN的要素如何适应慢性疾病：心肌梗死(MI)和慢性压力超负荷(PO)。拟议的实验将集中在ICN的两个特定适应：(1)神经元对神经调节剂反应的变化和(2)ICN网络效率的变化。我们还将评估靶向药物治疗减轻ICN不良重塑的疗效。利用豚鼠心脏神经丛的整体制备方法，我们将在对照组、MI和PO动物的组织中评估单个心脏内源性神经元对有和没有潜在神经调节剂的自主神经递质的生理反应，以表征应激诱导的神经元反应的变化。此外，我们将评估单个神经元对刺激迷走神经和节内纤维输入的输出，以评估综合网络功能。然后将比较未经治疗的疾病模型和使用标准疗法(如2受体阻断、AT受体抑制或抑制NO生成)治疗的疾病模型之间的神经元活动变化，以确定这些疗法是否调节ICN功能。 公共卫生相关性：这项提案将研究自主神经系统如何适应慢性心脏病，目标是开发更好的治疗慢性疾病的疗法。该项目将使用慢性心脏病的动物模型来检查疾病心脏自主神经系统内发生的变化，并评估心脏病的标准治疗方法如何影响这些过程。

DESCRIPTION (provided by applicant): Previous studies have shown that an imbalance in autonomic efferent neuronal tone, with reduced parasympathetic activity coupled with increased and heterogeneous sympathetic outflow, increases the risk of cardiac arrhythmias and sudden death. While the progression of cardiac disease affects multiple aspects of cardiac control, it is those changes in peripheral autonomic neuronal processing and their projections that ultimately determine the neuronal coordination of the heart. The intrinsic cardiac nervous system (ICN), the final common pathway for such neural control, integrates information from multiple inputs and mediates short- loop reflex control of regional cardiac indices. Although multiple studies have focused on cardiac stress- induced changes in post-ganglionic innervation patterns to the heart, little attention has been paid to the critical role of information processing within autonomic ganglia and how they remodel/adapt to imposed stress. It is our hypothesis that cardiac stress-induced adaptations within the ICN facilitate coordination of efferent parasympathetic output and that these changes are reflected in functional and phenotypic alterations in select intrinsic cardiac neuronal populations. These cardioprotective adaptations within the ICN could counteract, in part, the maladaptive effects of excessive sympatho-excitation associated cardiac stress. Numerous studies have identified molecular mechanisms associated with cardiac remodeling, including increased activity of the renin-angiotensin system, changes in nitric oxide (NO) production, and alterations in end-organ sensitivity to neurotransmitters. For each of these factors, while their direct effects on myocyte function are well established, recent data indicates that many of their cardiac effects are mediated via alterations in function within the cardiac nervous system. To specifically address these points this proposal will evaluate how the elements of the ICN adapt to chronic disease using two different animal models of heart disease: myocardial infarction (MI) and chronic pressure overload (PO). The proposed experiments will focus on two specific adaptations of the ICN: (1) changes in neuronal responses to neuromodulators and (2) changes in ICN network efficiency. We will also evaluate the efficacy of targeted pharmacologic therapy to mitigate adverse remodeling of the ICN. Using a whole mount preparation of the guinea pig cardiac plexus, we will evaluate the physiological responses of individual intrinsic cardiac neurons to autonomic neurotransmitters with and without potential neuromodulators, such as angiotensin II and NO in tissues from control, MI and PO animals to characterize stress-induced changes in neuronal responses. In addition, we will evaluate the output of individual neurons to stimulation of vagal and intraganglionic fiber inputs to evaluate integrated network function. Changes in neuronal activity will then be compared between untreated disease models and disease models treated with standard therapeutics such as 2-receptor blockage, AT receptor inhibition, or inhibition of NO generation, to determine if these therapies modulate the ICN function. PUBLIC HEALTH RELEVANCE: This proposal will examine how the autonomic nervous system adapts to chronic heart disease, with the goal of developing better therapeutics for the treatment of chronic disease. The project will use animal models of chronic heart disease to examine the changes that occur within the cardiac autonomic nervous system with disease as well as evaluating how standard therapies for cardiac disease affect these processes.