Regulation of neuro-cardiovascular function during stress

退伍军人的心血管发病率和死亡率高于普通人群，独立于 慢性病或社会经济状况等因素。抑郁症现在被认为是一种非传统的 心血管疾病的危险因素。近三分之一的退伍军人在某种程度上患有抑郁症， 不管他们是否被部署在战斗中。脑内血管加压素(AVP)受体的激活 中枢神经系统，特别是室旁核(PVN)与抑郁症有关。 最近的研究表明，AVP是从PVN内的树突释放出来的，中央AVP介导了 交感神经兴奋可观察到心力衰竭。交感神经兴奋也与更大的 心血管风险。值得注意的是，γ-氨基丁酸(GABA)典型地抑制交感神经兴奋。新的 有证据表明，GABA可能由于可塑性而对AVP信号起到矛盾的刺激作用 这发生在神经元内的氯离子浓度上。细胞内氯离子浓度为 通过转运氯离子的氯化钠共转运体1(NKCC1)控制氯离子的转运 进入细胞或排出氯离子的氯化钾共转运蛋白2(KCC2)。因此，我们 假设AVP激活PVN内的V1a受体(V1aR)和/或V1b受体(V1bR)以增加 动脉压、心率和交感神经活动从而有助于增强这些 抑郁症动物模型对急性应激的反应。将解决三个具体目标。具体而言 目的1，我们将使用药物抑制和基因敲除的siRNA方法来评估 外源性AVP激活V1aR或V1bR单独或联合导致动脉压、心脏 心率和RSNA，以及对急性应激的夸大反应。在特定的目标2中，我们将测试在 NKCC1或KCC2在PVN中的转运减弱甚至逆转GABA能抑制血流动力学和 RSNA在基础状态或急性应激时对V1aR和/或V1bR的激活做出反应。在具体目标3中，我们 将确定PVN内的内源性AVP是否激活V1aR和/或V1bR，从而促进 慢性不可预测应激(CMS)大鼠模型的动脉压和RSNA增加--一种有效的模型 以及通过NKCC1的运输增加或通过KCC2的运输减少是否阻止 GABA能抑制这些反应。我们将在有意识的、无拘无束的斯普拉格中测试这一假设 Dawley大鼠长期使用遥测发射器检测血流动力学和神经活动 测量。清醒大鼠不仅能遥测动脉血压，还能监测RSNA 已经被包括我们自己在内的少数几个实验室掌握，并为评估提供了一个强大的工具 在最小调查人员干预的情况下对基础和压力条件进行评估。我们将确定 加压素能受体(S)参与对外源性AVP和急性应激源的反应：空气喷射， 鼻咽反射、50°C水中的尾巴和束缚应力。然后我们将确定GABA抑制是否 阻断NKCC1或KCC2后，AVP信号转导发生改变。然后，我们将对大鼠进行CMS并评估 阻断V1aR和/或V1bR是否会降低基础动脉压、心率和RSNA。我们会 评估CMS是否易于对急性应激源做出更强的反应，以及这种反应是否源于 可能受GABA能系统可塑性影响的加压素能信号。带着激动人心的 已经在其他疾病的I期试验中的新的脑功能、高度选择性的V1aR拮抗剂的出现， 研究应激障碍中的V1aR和V1bR拮抗作用的必要性对于 治疗抑郁症等慢性应激患者。拟议的研究将提供关键的 设计临床试验所依据的理论基础和强有力的机械证据。鉴于我们的退伍军人 既有抑郁症的经历，又有心血管发病率和死亡率的高风险，建议的临床前 研究将为新的辅助治疗奠定重要基础，以改善抑郁症退伍军人的预后。

Cardiovascular morbidity and mortality is higher among Veterans than the general population independent of factors such as chronic illnesses or socio-econamic status. Depression is now recognized as a non-traditional risk factor for cardiovascular disease. Nearly one-third of Veterans suffer from depression at some point, regardless of whether they have been deployed in combat. Activation of vasopressin (AVP) receptors within the central nervous system, specifically the paraventricular nucleus (PVN) has been implicated in depression. Recent studies have shown that AVP is released from dendrites within the PVN and that central AVP mediates the sympathoexcitation observed heart failure. Sympathoexcitation is also strongly associated with greater cardiovascular risk. Notably, gamma-aminobutyric acid (GABA) typically suppresses sympathoexcitation. New evidence indicates that GABA may exert a paradoxically stimulatory effect on AVP signaling due to plasticity that occurs in the chloride ion concentration within neurons. The intracellular chloride concentration is controlled by chloride transport via the sodium chloride co-transporter 1 (NKCC1) which transports chloride ion into the cell or the potassium chloride co-transporter 2 (KCC2) which extrudes chloride ion. Thus, we hypothesize that AVP activates V1a receptors (V1aR) and/or V1b receptors (V1bR) within the PVN to increase arterial pressure, heart rate and sympathetic activity thereby contributing to the augmentation of these responses to acute stress in an animal model of depression. Three specific aims will be addressed. In Specific Aim 1, we will use pharmacologic inhibition and genetic knockdown with siRNA approaches to assess whether exogenous AVP activation of V1aR or V1bR alone or in combination results in increased arterial pressure, heart rate and RSNA and exaggerated responses to acute stress. In Specific Aim 2, we will test whether changes in NKCC1 or KCC2 transport in PVN attenuate, or even reverse, GABAergic inhibition of hemodynamic and RSNA responses to V1aR and/or V1bR activation in the basal state or during acute stress. In Specific Aim 3, we will ascertain whether endogenous AVP within the PVN activates V1aR and/or V1bR thereby contributing to the increased arterial pressure and RSNA in a rat model of chronic unpredictable stress (CMS), a validated model of depression, and whether increased transport via NKCC1 or decreased transport via KCC2 prevents GABAergic suppression of these responses. We will test this hypothesis in conscious, unrestrained Sprague Dawley rats chronically-instrumented with telemetry transmitters for both hemodynamic and nerve activity measurements. The ability to monitor not only arterial pressure but also RSNA by telemetry in conscious rats has been mastered by only a few laboratories including our own and provides a powerful tool for assessment of basal and stress conditions with minimal investigator interference. We will identify the contribution of the vasopressinergic receptor(s) involved in the responses to exogenous AVP as well as to acute stressors: air jet, nasopharyngeal reflex, tail in 50°C water, and restraint stress. We will then ascertain whether GABA inhibition of AVP signaling is altered by blockade of NKCC1 or KCC2. Then, we will subject the rats to CMS and assess whether blockade of V1aR and/or V1bR decreases baseline arterial pressure, heart rate and RSNA. We will evaluate whether CMS predisposes to enhanced responses to acute stressors and if that response is due to vasopressinergic signaling that may be impacted by plasticity of the GABAergic system. With the exciting advent of new brain-permeant, highly selective V1aR antagonists already in phase I trials in other disorders, the need for studying V1aR and V1bR antagonism in stress disorders is timely and distinctly translatable for treatment of people with chronic stress such as depression. The proposed studies will provide the crucial rationale and robust mechanistic evidence upon which to design a clinical trial. Given that our Veterans experience both depression and a high risk for cardiovascular morbidity and mortality, the proposed pre-clinical studies will lay a vital foundation for new adjunctive treatments to improve outcomes for depressed Veterans.