Live imaging of brain circuitry in mouse models of PTSD

描述（由申请人提供）：创伤后应激障碍（PTSD）小鼠模型中脑回路的实时成像创伤后应激障碍（PTSD）发生在经历危及生命的事件后，预计会影响许多退伍军人，但主要未满足的医疗需求是预测，诊断和治疗的可靠方法。患有PTSD的人显示脑功能解剖和脑结构的改变，许多人经历了选择性5-羟色胺再摄取抑制剂的缓解，将PTSD的解剖变化与肾上腺素能系统联系起来。遗传学研究表明，5-羟色胺转运体（SERT，5-HTT）基因多态性与包括创伤后应激障碍在内的情感障碍的风险有关。5-羟色胺代谢是压力激活的精神病理学的基础的证据来自三条研究线：1）啮齿动物模型，SERT的遗传改变或捕食者气味的恐惧刺激后; 2）人类SERT，SLC 6A 4的遗传解剖，以及等位基因与行为的关联; 3）人类受试者和小鼠模型的功能和结构磁共振成像（MRI）。我们的工作假设是，恐惧引起的神经活动在某些个体中在创伤事件解决后仍持续很长时间，导致中脑边缘皮层回路的功能解剖结构发生变化。我们进一步假设，当SERT水平较低和/或在生命早期经历创伤的成年人中发生持续的活动。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）测量恐惧对功能电路的影响;（3）量化早期生活创伤对成年人神经活动和中皮层边缘电路的影响。我们将测量恐惧前后的神经活动和电路变化，采用11.7T的定量锰增强MRI，提供90立方米的体素分辨率，以及DTI和组织学对解剖结构的影响。将对转基因小鼠（包括经验证的PTSD小鼠模型（SERT敲除）和其中50 kb小鼠SERT基因座已被人SERT等位基因（长或短变体）取代的新转基因小鼠）进行成像，并与野生型同窝仔进行比较。捕食者的气味将被用来引起恐惧反应。为了揭示SERT突变体是否影响共同的神经网络，将对具有与SERT突变体相似的行为表型的胆囊收缩素敲除小鼠进行成像和平行分析。将使用定制设计的计算软件，在体素基础上对每个基因型队列的3D全脑MR图像数据集进行统计学分析。这项研究是第一个将遗传学，功能和结构MRI与这种携带5-羟色胺转运体人类基因等位基因的新转基因小鼠模型的恐惧反应联系起来的研究。成功完成这项拟议的临床前研究将通过确定以下方面提供解决未满足需求所需的信息：a）预测风险的遗传易感性;和B）PTSD进展期间大脑功能变化的顺序，以设计阶段特异性诊断和治疗干预。

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.