Longitudinal Imaging of Frontal Cortex Afferents in a Mouse Model of Anxiety

描述（由申请人提供）：改变活动依赖回路形成的遗传变异可能导致回路发育中经验依赖的不平衡。脑源性神经营养因子（BDNF）是一种参与神经过程发育成熟和细胞存活的神经营养因子。20-30%的高加索人携带BDNF基因多态性，其中密码子66从缬氨酸变为蛋氨酸（Shimizu et al., 2004），这一变化已被证明会改变BDNF的活性调控释放（Chen et al., 2006）。BDNF val66met多态性与焦虑和抑郁有关（尽管并非没有争议），在早期生活压力最大的人群中相关性更强（Gatt等人，2009）。我们假设拥有BDNF的met66等位基因的个体削弱了海马旁体对扣带区的输入，而早期生活压力增强了杏仁核对扣带区的输入。我们假设额叶皮层投射的不平衡会影响情感体验和行为。在这一过程的动物模型中，（海马旁）外周（PRH）扣带事件的不发达使基底外侧杏仁核（BLA）扣带事件的增强、竞争性发展，导致涉及动作选择和认知控制的额叶回路中伤害避免信息的异常优势。我们提出了一个PRH:BLA扣带投射失衡，有多种原因，可能是焦虑和寻求新奇的一系列障碍的基础。我们将验证BDNF met66变异小鼠表现出焦虑增强的假设（Chen et al. 2006）也表现出PRH和BLA输入到扣带皮层的不平衡发育。为了探究这种假定的焦虑内表型，我们将使用最先进的突触形成纵向体内成像（Aim 1）和光遗传学工具（Aim 2）来探索BDNF敲敲小鼠从PRH和BLA到扣带皮层的远程传入事件的青春期发育（Chen等人，2006）。具体测量将包括体内扣带脊柱和PRH和BLA钮扣的周转率和密度（Aim 1），扣带中BLA和PRH传入所驱动的兴奋电流和抑制电流的比值，以及PRH和BLA扣带的平均AMPA:NMDA比值（Aim 2）。我们还将研究青少年应激和认知训练对PRH和BLA传入事件的可塑性（Aim 1）和连通性（Aim 2）的影响。我们预测，在涉及PRH和扣带的任务中进行认知训练将防止PRH:BLA失衡的发展并减少焦虑行为。我们的实验将有助于理解焦虑和伤害回避障碍的发育病因，提供一种可能转移到人类研究的内表型，并测试认知疗法的形式，以重新平衡神经回路的发展。7. 过度焦虑或它的对立面，低伤害规避，可以深刻地扰乱人类的生活。在我们的模型中，异常的青少年发育导致输入缺乏平衡，这些输入将安全和危险的信息传递给额叶皮层，对决策产生不利影响。我们将测试这个模型，以阐明焦虑和伤害回避障碍的发育原因，提供一种可以转移到人类研究的生物学测量，并测试认知疗法的形式，以修复这些回路中的不平衡。

DESCRIPTION (provided by applicant): Genetic variation that alters activity-dependent circuit formation may contribute to an experience-dependent imbalance in circuit development. Brain derived neurotrophic factor (BDNF) is a neurotrophic factor involved in developmental maturation of neural processes and cell survival. 20-30% of Caucasians carry a polymorphism in the BDNF gene, where codon 66 is altered from a valine to methionine (Shimizu et al., 2004), a change which has been shown to alter activity regulated release of BDNF (Chen et al., 2006). The BDNF val66met polymorphism has been linked to anxiety and depression (although not without controversy), with stronger correlation in persons who have had the greatest amount of early life stress (Gatt et al., 2009). We hypothesize that individuals possessing the met66 allele of BDNF have weakened parahippocampal inputs to the cingulated and that early life stress enhances amygdala inputs to the cingulated. We hypothesize an imbalance in projections to the frontal cortex biases emotional experience and behaviors. In our animal model of this process, underdevelopment of the (parahippocampal) perirhinal (PRH) cingulated afferents enable enhanced, competitive development of the basolateral amygdala (BLA) cingulated afferents leading to abnormal dominance of harm avoidance information in frontal circuits involved in action selection and cognitive control. We propose a PRH:BLA cingulated projection imbalance, with diverse causes, may underlie a range of disorders in the spectrum of anxiety and novelty seeking. We will test the hypothesis that BDNF met66 variant mice which show enhance anxiety (Chen et al. 2006) also show unbalanced development of PRH and BLA inputs to the cingulated cortex. To pursue this putative endophenotype of anxiety, we will use state of the art longitudinal in vivo imaging of synapse formation (Aim 1) and optogenetic tools (Aim 2) to probe the adolescent development of long range afferents from the PRH and BLA to the cingulated cortex in BDNF val66met knocking mice (Chen et al., 2006). Specific measures will include in vivo cingulated spine and PRH and BLA bouton turnover and density (Aim 1), the ratio of excitatory and inhibitory currents driven by the BLA and PRH afferents in the cingulated, and the average PRH- and BLA-cingulated AMPA:NMDA ratio (Aim 2). We will also investigate the effects adolescent stress and cognitive training on plasticity (Aim 1) and connectivity (Aim 2) of PRH and BLA afferents. We predict that cognitive training in tasks that engage the PRH and the cingulated together will protect against the development of PRH:BLA imbalance and reduce anxiety behavior. Our experiments will inform understanding of the developmental etiology of disorders of anxiety and harm avoidance, provide an endophenotype that may be transferred to human studies, and test forms of cognitive therapy to rebalance circuit development. 7. Project Narrative Excess anxiety or its opposite, low harm avoidance, can profoundly disrupt human lives. In our model, abnormal juvenile development leads to a lack of balance in inputs that relay information about safety and danger to the frontal cortex adversely affecting decision making. We will test this model to illuminate the developmental causes of disorders of anxiety and harm avoidance, provide a biological measure that can be transferred to human studies, and test forms of cognitive therapy to repair an imbalance in these circuits.