A Model and Mechanism of the Comorbid Interaction between Pain and Anxiety

描述（由申请人提供）：疼痛通常伴有临床合并症，如焦虑和抑郁。然而，大多数临床前模型并没有检查这些合并症对疼痛的影响。例如，虽然流行病学研究一直表明疼痛和焦虑之间存在共病关系，但由于缺乏临床前模型，焦虑对从急性疼痛过渡到慢性疼痛的影响仍然未知。为了建立疼痛和焦虑的临床前模型，我们最近在一组初步实验中证明，焦虑样行为（升高加上迷宫，暗灯箱试验）可诱导周围神经损伤引起的持久而非短暂的伤害感觉大鼠。焦虑样行为的存在延长并加剧了伤害性行为。此外，在那些表现出伤害性和焦虑样行为的大鼠的杏仁核中，神经肽S （NPS，一种具有内源性抗焦虑特性的新型神经肽）的表达下调，与基础和刺激诱发神经活动（fMRI）增加有关。脑室内外源性NPS同时改善了同一大鼠的伤害性和焦虑样行为。这些初步结果表明，焦虑样行为对慢性疼痛的转变有重要影响，并表明中枢NPS系统可能在疼痛和焦虑之间的共病相互作用中发挥关键作用。在本次拨款申请中，我们建议建立一个伤害性和焦虑样行为联合的大鼠模型，并使用该模型来a)评估从急性到慢性疼痛过渡期间焦虑样行为的贡献，b)确定中枢NPS系统在疼痛和焦虑共病相互作用中的作用。我们将通过使用行为学和药理学工具、免疫组织化学、Western blot、实时PCR、原位杂交、细胞培养、ELISA、膜片钳记录和啮齿动物功能MRI （fMRI）来实现这一目标。在具体目标1中，我们将评估伤害感受诱导的焦虑与基因预先处理的焦虑对大鼠短暂性（皮下注射角叉菜胶）或持续性（精神神经损伤）伤害感受后伤害行为和脑神经活动（啮齿动物功能磁共振成像）的影响。在具体目标2中，我们将使用NPS和NPSR （NPS受体）敲除小鼠，研究中枢NPS系统在伤害性和焦虑样行为中的功能作用。在具体目标3中，我们将通过确定NPS对以下方面的影响来研究疼痛和焦虑之间相互作用的神经和细胞机制：a)与伤害性加工和情绪/情感反应相关的大脑区域的神经活动（啮齿动物功能磁共振成像）；b)杏仁核内NPS- gaba连接有助于调节焦虑障碍（膜片钳记录和细胞培养）。我们预计该项目将a)建立一个有用的临床前模型，用于研究焦虑对从急性到慢性疼痛过渡的影响；b)提出通过调节中枢NPS系统同时治疗疼痛和焦虑的策略。

DESCRIPTION (provided by applicant): Pain is often complicated by clinical comorbidities such as anxiety and depression. Most preclinical models, however, do not examine the impact of such comorbidities on pain. For example, while epidemiological studies have consistently shown a comorbid relationship between pain and anxiety, the impact of anxiety on the transition from acute to chronic pain remains unknown largely due to the lack of preclinical models. In an effort to establish a preclinical model of combined pain and anxiety, we recently demonstrated in a set of preliminary experiments that anxiety-like behavior (elevated plus maze, dark-light box test) was induced in rats with persistent, but not transient, nociception from peripheral nerve injury. The presence of anxiety-like behavior prolonged and exacerbated nociceptive behavior. Furthermore, the expression of neuropeptide S (NPS, a novel neuropeptide with an endogenous anxiolytic property) was downregulated, associated with increased basal and stimulation-evoked neural activities (fMRI), in the amygdala of those rats exhibiting nociceptive and anxiety-like behavior. Intracerebroventricular administration of exogenous NPS concurrently improved nociceptive and anxiety-like behavior in the same rats. These preliminary results demonstrate a significant impact of anxiety-like behavior on the transition to chronic pain and suggest that the central NPS system may play a critical role in the comorbid interaction between pain and anxiety. In this grant application, we propose to establish a rat model of combined nociceptive and anxiety-like behavior and use this model to a) evaluate contributions of anxiety-like behavior during the transition from acute to chronic pain and b) determine the role of the central NPS system in the comorbid interaction between pain and anxiety. We will achieve this goal by using behavioral and pharmacological tools, immunohistochemistry, Western blot, real-time PCR, in situ hybridization, cell culture, ELISA, patch-clamp recording, and rodent functional MRI (fMRI). In Specific Aim 1, we will evaluate the impact of nociception-induced vs. genetically pre-disposed anxiety on nociceptive behavior and brain neural activities (rodent fMRI) following transient (subcutaneous carrageenan injection) or persistent (mental nerve injury) nociception in rats. In Specific Aim 2, we will examine a functional role for the central NPS system in nociceptive and anxiety-like behavior using NPS and NPSR (NPS receptor) knockout mice. In Specific Aim 3, we will investigate the neural and cellular mechanism underlying the interaction between pain and anxiety by determining the effect of NPS on a) neural activities in the brain regions implicated in nociceptive processing and emotional/affective response (rodent fMRI) and b) an intra-amygdaloid NPS-GABA link contributory to the regulation of anxiety disorder (patch-clamp recording and cell culture). We anticipate that this project will a) establish a preclinical model useful to examine the impact of anxiety on the transition from acute to chronic pain and b) suggest a strategy for the concurrent treatment of pain and anxiety by regulating the central NPS system. PUBLIC HEALTH RELEVANCE: Despite recent progresses in basic science research of pain and pain modulation, it remains very difficult to treat chronic pain and the related clinical comorbidities. Currently, most preclinical models do not reflect the impact of pain-related comorbidities on the transition from acute to chronic pain. The outcome of this study will establish a preclinical model of combined pain and anxiety and suggest a new therapeutic option for the concurrent treatment of both pain and anxiety.