Live imaging of brain circuitry in mouse models of PTSD

描述(申请人提供)：创伤后应激障碍(PTSD)小鼠模型的脑电路实时成像发生在经历了危及生命的事件后，预计会影响许多归来的退伍军人，但一个主要的未得到满足的医学需求是对可靠的预测、诊断和治疗方法的需求。PTSD患者表现出大脑功能解剖和脑结构的变化，许多人从选择性5-羟色胺再摄取抑制剂中获得缓解，将PTSD的解剖变化与5-羟色胺能系统联系起来。遗传学研究表明，5-羟色胺转运体(SERT，5-HTT)基因的多态与包括创伤后应激障碍在内的情感障碍的风险有关。5-羟色胺代谢是应激激活精神病理学的基础的证据来自三个方面的研究：1)具有SERT基因改变的啮齿动物模型，或在具有捕食者气味的恐惧刺激后的模型；2)人类SERT、SLC6A4的基因解剖，以及等位基因与行为的关联；以及3)人类受试者和小鼠模型的磁共振成像(MRI)，包括功能和结构。我们的工作假设是，恐惧唤起了神经活动，在某些人中，这种活动在创伤事件解决后很长一段时间内仍在继续，导致中脑边缘皮质回路的功能解剖发生变化。我们进一步假设，持续活动发生在SERT水平较低和/或在生命早期经历过创伤的成年人中。我们的具体目标是：(1) 绘制并测量野生型和SERT突变体对恐惧的神经反应的强度和持续时间；(2)测量恐惧对功能回路的影响；以及(3)量化早期生活创伤对成人神经活动和中皮质边缘回路的影响。我们将以时间推移的方式测量恐惧前后的神经活动和电路变化，并使用DTI和组织学来测量在11.7T下给予90？m~3体素分辨率的活体小鼠的定量锰增强MRI，以及对解剖学的影响。转基因小鼠，包括经过验证的PTSD(SERT基因敲除)小鼠模型，以及新的转基因小鼠，其中50kb的小鼠SERT基因座已被人类SERT等位基因(长或短变异)取代，将被成像并与野生型窝种进行比较。捕食者的气味将被用来激发恐惧反应。为了揭示SERT突变是否会影响常见的神经网络，将对行为表型与SERT突变相似的CCK基因敲除小鼠进行成像和平行分析。来自每个基因型队列的3D全脑MR图像的数据集将使用定制的计算软件以体素为基础进行统计分析。这项研究首次将遗传学、功能和结构核磁共振与恐惧反应联系起来，在这种新的携带人类5-羟色胺转运体基因等位基因的转基因小鼠模型中。这项拟议的临床前研究的成功完成将提供必要的信息，通过确定：a)预测风险的遗传易感性；以及b)发展为创伤后应激障碍的过程中大脑功能变化的序列，以设计特定阶段的诊断和治疗干预措施，以满足未得到满足的需求。

DESCRIPTION (provided by applicant): Live imaging of brain circuitry in mouse models of PTSD Post-traumatic stress disorder (PTSD) occurs after experiencing a life-threatening event and is predicted to affect many returning veterans, yet a major unmet medical need is for reliable methods of prediction, diagnosis and treatment. People with PTSD display alterations in brain functional anatomy and in brain structures, and many experience relief from selective serotonin reuptake inhibitors, linking anatomical changes in PTSD to the serotonergic system. Genetic studies show an association with polymorphisms in the serotonin transporter (SERT, 5-HTT) gene with risk of affective disorders including PTSD. Evidence that serotonin metabolism underlies stress-activated psychopathologies comes from three lines of research: 1) Rodent models, with genetic alterations of SERT or after fear provocation with predator odor; 2) Genetic dissection of human SERT, SLC6A4, and association of alleles with behavior; and 3) Magnetic resonance imaging (MRI), both functional and structural, of human subjects and mouse models. Our working hypothesis is that fear evokes neural activity that in some individuals continues long after the traumatic event resolves, leading to changes in functional anatomy of the mesolimbic cortical circuit. We further hypothesize that persistent activity occurs when SERT levels are low and/or in adults who experienced trauma early in life. Our specific aims are to: (1) Map and measure the intensity and duration of neural responses to fear in wild-type and SERT mutants; (2) Measure the impact of fear on functional circuitry; and (3) Quantify effects of early life trauma on neural activity and mesocortical limbic circuitry in the adult. We will measure the neural activity and circuitry changes before and after fear with time-lapse, quantitative manganese-enhanced MRI of living mice at 11.7T giving 90¿m3 voxel resolution, and the effects on anatomy with DTI and histology. Transgenic mice, including the validated mouse model of PTSD (SERT knock-out), and new transgenics in which 50kb of the mouse SERT locus has been replaced with human SERT alleles (long or short variants), will be imaged and compared with wild-type littermates. Predator odor will be used to provoke fear responses. To reveal whether SERT mutants affect a common neural network, cholecystokinin knock-out mice with a behavioral phenotype similar to SERT mutants will be imaged and analyzed in parallel. Datasets of 3D whole brain MR images from cohorts of each genotype will be analyzed statistically on a voxel-wise basis with custom-designed computational software. This study is the first to link genetics, functional and structural MRI with fear responses in this new transgenic mouse model carrying human gene alleles of the serotonin transporter. The successful completion of this proposed preclinical study will provide information necessary to address the unmet need by identifying: a) genetic susceptibilities for prediction of risk; and b) sequence of functional changes in the brain during progression to PTSD for design of stage-specific diagnoses and therapeutic interventions.