Serotonergic modulation of excitatory synapse formation and maturation during development

项目摘要 自闭症谱系障碍(ASD)包括一组典型的严重神经发育障碍 由沟通障碍和社会损害造成。鉴于症状出现在3岁之前，它是 大部分人都同意，神经元功能障碍发生在大脑发育的早期。发育中的大脑显示出 对经验的塑性变化的非凡能力；因此，它的发展最容易受到 环境因素会破坏正常的大脑功能。宫内暴露于升高血液5-羟色胺的药物 水平，包括选择性5-羟色胺再摄取抑制剂(SSRI)，已经显示出行为和心理上的 在动物模型和人类研究中，后代的缺陷与自闭症症状非常相似。按顺序 要了解这些变化是如何发生的，有必要首先了解 5-羟色胺能调节大脑功能。兴奋性突触的形成和稳定是已知的 对于最初建立功能神经回路来说是必不可少的。相反，突触发育受阻 损害神经元功能，被认为是多种神经发育障碍的病理基础。PFC 由5-羟色胺能轴突终末密集支配，并与可能 在自闭症等疾病中受到干扰。尽管有大量文献研究了5-羟色胺在调节 在脑部疾病的行为和发病机制方面，在细胞和分子水平上对 5-羟色胺在早期皮质发育中的作用，特别是在突触后调节5-羟色胺的机制 发育中的PFC中突触的发育。在本研究中，我们使用了一种新的工具组合 包括能够精确释放5-羟色胺和谷氨酸神经递质的双色、双光子灌输， 5-羟色胺基因定位神经元的钙成像、电生理和光遗传刺激以测试OUR 中心性假说认为5-羟色胺信号促进兴奋性突触形成并控制 脑发育过程中兴奋性突触的成熟。在强劲的初步数据指引下，我们将审查 这一假说有两个具体目的：1)确定5-羟色胺信号在降低诱导阈值中的作用 依赖活动的突触形成。2)定义5-羟色胺对依赖活动、特定输入和 异位脊椎稳定。这些研究的结果将进一步加深我们对独特和 5-羟色胺调节大脑发育的详细机制，与细胞基础密切相关 神经发育障碍。在美国，大约13%的孕妇使用SSRI，这通常是 提高胎儿5-羟色胺水平。我们预计，我们的结果将突出调查的新途径 5-羟色胺信号早期扰动引起的神经发育障碍的病理生理学基础。

Project Summary Autism Spectrum Disorders (ASDs) comprise a group of severe neurodevelopmental disorders that are typified by communication deficits and social impairment. Given that the onset of symptoms occurs by the age of 3, it is largely agreed that neuronal dysfunction arises during early brain development. A developing brain shows a remarkable capacity for plastic changes in response to experiences; thus, its development is most vulnerable to the environmental factors that can derail normal brain function. In utero exposure to drugs that raise blood 5HT levels, including selective serotonin reuptake inhibitors (SSRIs), has demonstrated behavioral and psychological deficits in offspring that closely resemble autistic symptoms in both animals models and human studies. In order to understand how these alterations arise, it is necessary to first understand the basic mechanisms of serotonergic modulation of brain function. Formation and stabilization of excitatory synapses are known to be essential for the initial establishment of functional neural circuits. Conversely, disrupted synapse development impairs neuron function and is thought to underlie the pathology of multiple neurodevelopmental disorders. PFC is densely innervated by serotonergic axon terminals and associated with higher cognitive processes that may be disrupted in illnesses such as ASDs. Despite a wealth of literature examining the role of 5HT in modulating behavior and in the pathogenesis of brain disorders, little is known at the cellular and molecular level about the role of 5HT in early cortical development, and particularly the postsynaptic 5HT mechanisms that modulate synapse development in the developing PFC. In the present study, we utilize a novel combination of tools including two-color, two-photon uncaging that enables precise release of 5HT and glutamate neurotransmitters, calcium imaging, electrophysiology, and optogenetic stimulation of genetically-targeted 5HT neurons to test our central hypothesis that 5HT signaling promotes the initiation of excitatory synapse formation and controls the maturation of excitatory synapses during brain development. Guided by strong preliminary data, we will examine this hypothesis in two specific aims: 1) Determine the role of 5HT signaling in lowering the threshold for induction of activity-dependent synapse formation. 2) Define the actions of 5HT on activity-dependent, input-specific and heterosynaptic spine stabilization. Results from these studies will further our understanding of the unique and detailed mechanisms by which 5HT regulates brain development, with critical relevance to cellular underpinnings of neurodevelopmental disorders. In the U.S., approximately 13% of pregnant women use SSRIs, which typically increase fetal 5HT levels. We expect that our results will highlight new avenues into the investigation of the pathophysiology underlying neurodevelopmental disorders resulting from early perturbation of 5HT signaling.