The Role of Habenular Hyperactivity in the Action of Tianeptine, a Novel Treatment for Neuropathic Pain

项目总结/摘要 神经病理性疼痛（neuropathic pain，NP）是指躯体感觉器官损伤或疾病后的慢性疼痛 导致疼痛和情感症状的神经系统。主要的治疗方法是单胺靶向 抗抑郁药，大约一半的患者对它没有反应。一种叫噻奈普汀的非典型抗抑郁药 (TIA)我们的实验室发现它是一种莫尔激动剂，但与其他阿片类药物不同的是，它缺乏欣快感 质量，代谢迅速离开身体，并且在临床剂量下均未显示耐受性/戒断作用。 初步数据表明，TIA减少了来自NP的异常性疼痛，而没有快速耐受性，如在2010年12月的研究中所观察到的。 吗啡TIA是如何以及在何处缓解这些症状的尚不清楚。一个候选区域是 缰核（Hb），在慢性疼痛中失调，对几种单胺有抑制性输出 调节区域。通常，血红蛋白中的神经元会对厌恶刺激做出反应，抑制这些反应。 下游奖励途径。在慢性疼痛下，该区域变得过度活跃。一个选择是， 发生与缰核有树突莫尔在脑内表达有关。MORs通常 抑制，并通过释放内源性阿片样物质激活。然而，在慢性疼痛期间， 变得失调，并且在许多区域，MORs的表达或可用性降低。我假设 与异常性疼痛和快感缺乏增加相关的Hb病理性活动过度至少 部分原因是慢性疼痛条件下莫尔表达或可用性降低， TIA管理将使该区域的活动正常化，与NP行为减少相关。为了 为了解决这个问题，我将使用NP的备用神经损伤模型（SNI），该模型引起疼痛和情感 症状，包括异常性疼痛和快感缺乏。在目标1中，我将检验缰核过度活跃是 与莫尔活性的变化有关，噻奈普汀使NP中的缰活性正常化。在1.A中，我将 在SNI和假手术对照雄性和雌性MOR-Cre小鼠中进行纤维光度测定。我会测量钙 在异常性疼痛和快感缺乏的测量过程中，Hb中的总体和莫尔表达细胞的活性。在 1.B，我将长期治疗TIA动物，并观察这是否会导致神经和/或行为的逆转。 SNI和对照小鼠之间的差异。在目标2中，我将检查分子和转录变化， 通过比较来自假手术/载体的缰组织， SNI/媒介物、假手术/TIA和SNI/TIA小鼠。在2.A中，我将使用蛋白质连接测定来检查 在2.B中，我将分析scRNAseq数据，以获得广泛的转录水平和区域细节，以及莫尔表达。 疼痛和噻奈普汀诱导的变化，共表达模式在不同条件下如何变化。这将 请允许我观察莫尔共表达的比例是否发生变化，就像在对已发表的 观察不可避免的急性休克后缰核的数据。到目前为止，还没有研究着眼于缰核， 神经性疼痛期间的MOR。

Project Summary/Abstract Neuropathic pain (NP) is defined as chronic pain following injury or disease in the somatosensory nervous system resulting in pain and affective symptoms. The primary treatments are monoamine targeting antidepressants, which roughly half of patients do not respond to. An atypical antidepressant called tianeptine (TIA) was discovered by our lab to be an MOR agonist, but differs from other opioids by lacking euphoric quality, metabolizing rapidly out of the body, and not showing tolerance/withdrawal effects all at clinical doses. Preliminary data indicates that TIA reduces allodynia from NP, without rapid tolerance as observed in morphine. How and where TIA is acting to relieve these symptoms is unclear. One candidate region is the habenula (Hb), which is dysregulated in chronic pain, and has inhibitory outputs to several monoamine regulating regions. Typically, neurons in the Hb fire in response to aversive stimuli, inhibiting those downstream reward pathways. Under chronic pain, the region becomes hyperactive. One option for how this happens relates to the habenula having the densest MOR expressing in the brain. MORs are typically inhibitory, and activated by the release of endogenous opioids. However, during chronic pain this system becomes dysregulated and, in many regions, MORs decrease in expression or availability. I hypothesize that pathological hyperactivity in the Hb, which is associated with an increase in allodynia and anhedonia, is at least partially due to a decrease in MOR expression or availability under conditions of chronic pain, and that chronic TIA administration will normalize activity in the region, correlating with decreased NP behaviors. In order to address this, I will use the spared nerve injury model (SNI) of NP, which induces both painful and affective symptoms, including allodynia and anhedonia. In Aim 1, I will test the hypothesis that habenula hyperactivity is related to changes in MOR activity, and that tianeptine normalizes habenular activity in NP. In 1.A, I will perform fiber photometry in SNI and sham control male and female MOR-Cre mice. I will measure calcium activity in both global and MOR expressing cells in the Hb, during measures of allodynia and anhedonia. In 1.B, I will chronically treat animals with TIA, and observe if this results in reversal of neural and/or behavioral disparities between SNI and control mice. In Aim 2, I will examine the molecular and transcriptional changes caused by NP and following chronic TIA treatment by comparing habenular tissue from sham/vehicle, SNI/vehicle, sham/TIA, and SNI/TIA mice. In 2.A, I will use a protein ligation assay to examine changes in MOR expression with regional detail, and in 2.B, I will analyze scRNAseq data for both broad transcriptional changes induced by pain and tianeptine, how co-expression patterns change between conditions. This will allow me to observe if the ratio of MOR co-expression shifts, as it did in preliminary re-analysis of published data looking at the habenula following acute unavoidable shock. To date, no studies have looked at habenular MORs during neuropathic pain.