Serotonergic modulation of excitatory synapse formation and maturation during development

项目摘要 自闭症谱系障碍（ASD）包括一组严重的神经发育障碍， 沟通障碍和社交障碍鉴于症状的发作发生在3岁， 大多数人同意神经元功能障碍发生在大脑发育的早期。一个发育中的大脑 塑料变化的显着能力，以应对经验;因此，它的发展是最容易受到 会破坏正常大脑功能的环境因素子宫内暴露于升高血液5 HT的药物 水平，包括选择性5-羟色胺再摄取抑制剂（SSRIs），已证明行为和心理 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。为了 要了解这些变化是如何发生的，首先需要了解这些变化的基本机制。 脑功能的多巴胺能调节。兴奋性突触的形成和稳定是已知的， 对于功能性神经回路的初步建立至关重要。相反，突触发育中断 损害神经元功能，并被认为是多种神经发育障碍的病理基础。PFC 由神经元轴突末梢密集支配，并与高级认知过程相关， 在自闭症等疾病中会受到干扰。尽管有大量的文献研究了5-HT在调节细胞凋亡中的作用， 行为和大脑疾病的发病机制，在细胞和分子水平上对大脑疾病的发病机制知之甚少。 5-HT在早期皮质发育中的作用，特别是调节皮质发育的突触后5-HT机制。 在本研究中，我们利用一种新的工具组合， 包括双色、双光子撑开，能够精确释放5-HT和谷氨酸神经递质， 钙成像，电生理学和遗传靶向的5 HT神经元的光遗传学刺激，以测试我们的 一个中心假设，即5 HT信号促进兴奋性突触形成的启动，并控制 大脑发育过程中兴奋性突触的成熟在强有力的初步数据的指导下，我们将研究 这一假说有两个具体的目的：1）确定5 HT信号在降低诱导阈值中的作用 活动依赖性突触的形成。2)定义5 HT对活动依赖性、输入特异性和 异突触棘稳定。这些研究的结果将进一步加深我们对独特和 5-HT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SSRIs， 增加胎儿5 HT水平。我们希望我们的研究结果将突出新的途径， 病理生理学潜在的神经发育障碍所造成的早期扰动的5 HT信号。

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.