Pronociceptive and antinociceptive opioid mechanisms in the central nucleus of the amygdala

项目摘要 多条证据支持大脑回路中广泛存在的结构和功能适应不良 促进慢性疼痛的促成因素。下行痛觉调制回路的失调 在慢性疼痛患者中表现出来。然而，我们对分子机制和大脑的理解 在正常和病理条件下，作为抑制或促进疼痛的基础的回路仍然有限。 阿片类镇痛剂参与了这些大脑回路，但治疗疼痛的非成瘾选择是迫切需要的。 在这项提案中，我们将研究杏仁核中的痛觉调制机制，杏仁核是一种参与 整合疼痛相关的感觉输入和情绪处理。我们将检验这一假设在功能上 杏仁中央核内源性MU(MOR)和KAPPA(KOR)阿片环路的对立 分别抑制或促进疼痛行为。双向下行疼痛调制电路已经被 其特点是最广泛地位于延髓头端腹内侧(RVM)。然而，人们对此知之甚少。 脑干上方下行的调制回路。RVM中的伤害性感受和抗伤害性感受功能 是由表达MOR的“疼痛”细胞和表达KOR的“疼痛关闭”细胞介导的。我们建议类似的 MOR和KOR表达细胞在感觉和/或情感中为对手角色服务的功能组织 疼痛行为也存在于CEA中。重要的是，MOR和KOR电路的倒数函数可以 代表了大脑其他区域疼痛调制的一般组织原则。 我们将结合光遗传和化学遗传方法使用转基因小鼠模型和 顺行和逆行追踪用于MOR和KOR的细胞类型特异性和投影特异性分析 在神经病理性疼痛模型(脊神经结扎)中CEA中的回路及其对疼痛行为的贡献。 具体目标1将确定CEA内KOR和MOR细胞的解剖学特征。具体目标2 将探讨KOR和MOR激活或抑制的突触和细胞效应及其相互作用。 具体目标3将使用反射反应来评估MOR和KOR环路在疼痛行为中的作用 (机械和热阈值)以及与情感和动机品质有关的复杂行为 疼痛(发声、条件性位置偏爱/回避)。电生理和行为结果将 在控制条件下用细胞特异性操作进行评估，并在神经病理性疼痛模型中 雄性和雌性小鼠可以确定杏仁核回路中可能存在的性别差异。 这项拟议的研究将确定一个以前未知的KOR介导的杏仁核伤害感受前回路及其 与吗啡介导的抗伤害性机制的关系。MOR信号受损和/或KOR增加 CEA中的信号可能导致抑制-兴奋失衡的下行调制，以促进慢性 疼痛。重要的是，CEA中相反的MOR-KOR功能将为 慢性疼痛的非成瘾疗法的发展。

Project Summary Multiple lines of evidence support wide-spread structural and functional maladaptations in brain circuits as a contributing factor promoting chronic pain. Dysregulation of descending pain modulatory circuits have been demonstrated in chronic pain patients. However, our understanding of the molecular mechanisms and brain circuits that underlie inhibition or facilitation of pain under normal and pathological conditions remains limited. Opioid analgesics engage these brain circuits, but non-addictive options to treat pain are urgently needed. In this proposal, we will investigate pain modulatory mechanisms in the amygdala, a structure involved in integration of pain-related sensory inputs and emotional processing. We will test the hypothesis that functionally opposing endogenous mu (MOR) and kappa (KOR) opioid circuits in the central nucleus of the amygdala (CeA) inhibit or promote, respectively, pain behavior. Bidirectional descending pain modulatory circuits have been characterized most extensively in the rostral ventromedial medulla (RVM). However, little is known about descending modulatory circuits above the brainstem. In the RVM, pro-nociceptive and anti-nociceptive functions are mediated by MOR-expressing “pain ON” cells and KOR-expressing “pain OFF” cells. We propose that similar functional organization with MOR- and KOR-expressing cells serving opponent roles in sensory and/or affective pain behavior also exists in the CeA. Importantly, the reciprocal function of the MOR and KOR circuits may represent a general organizational principle for pain modulation in other brain areas. We will use transgenic mouse models in combination with optogenetic and chemogenetic approaches and anterograde and retrograde tracing for the cell type-specific and projection-specific analysis of MOR and KOR circuits in the CeA and their contribution to pain behaviors in a neuropathic pain model (spinal nerve ligation). Specific Aim 1 will determine the anatomical characteristics of KOR and MOR cells in the CeA. Specific Aim 2 will explore the synaptic and cellular effects of KOR and MOR activation or inhibition and their interaction. Specific Aim 3 will assess the role of MOR and KOR circuits in pain behaviors using reflexive responses (mechanical and thermal thresholds) as well as complex behaviors related to affective and motivational qualities of pain (vocalization, conditioned place preference/avoidance). Eletrophysiological and behavioral outcomes will be assessed with cell specific manipulations under control conditions and in a neuropathic pain model in both male and female mice allowing the determination of possible sex differences in the amygdala circuit. The proposed studies will identify a previously unknown KOR-mediated pro-nociceptive amygdala circuit and its relationship to MOR-mediated anti-nociceptive mechanisms. Impaired MOR signaling and/or increased KOR signaling in the CeA may result in an inhibition-excitation imbalance of descending modulation to promote chronic pain. Importantly, the opposing MOR-KOR function in the CeA would provide the conceptual basis for the development of non-addictive therapies for chronic pain.