The effects of anesthetics on brain development

麻醉药对大脑发育的影响

• 批准号: 8788865
• 负责人: Cyrus David Mintz
• 金额: $ 11.28万
• 依托单位: JOHNS HOPKINS UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-02-01 至 2017-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8788865
• 关键词: effects; anesthetics; brain; development

DESCRIPTION (provided by applicant): Epidemiologic studies demonstrate an association between childhood exposure to anesthesia and an increase in subsequent learning and behavioral disorders. These data are complemented by animal studies showing that rat pups exposed to anesthetics exhibit lasting deficits in learning. Previous investigators have demonstrated that anesthetic agents can increase apoptosis in the developing brain, but little has been done to assess the effects of anesthetics on the development of the neurons that remain. Our preliminary data raise a concern that some commonly used anesthetics presented at clinically relevant doses may interfere with the response of axonal growth cones to the cues that guide them to the correct dendritic targets, thus potentially disrupting the formation of brai circuits critical for higher functions, such as learning. In this proposal we will examine the effets of the major classes of anesthetic agents on axon guidance and circuit formation, with a view towards discovering mechanisms of this deleterious effect and determining how anesthetic plans may be designed to avoid or minimize it. The Specific Aims are: (1) Test the effects of general anesthetic agents on the response of axonal growth cones to guidance cues. The hypothesis to be tested is that anesthetic agents with activity at GABAA receptors and/or NMDA receptors can substantially interfere with growth cone function, including sensing of and response to guidance cues. Using time-lapse microscopy and quantitative analysis of axon morphology we will determine the effects of the major classes of anesthetic agents on axonal growth cone motility in the absence of guidance cues. Then, using a collapse assay and gradient turning assay, we will test whether anesthetics interfere with the response of the axonal growth cone to repulsive and attractive guidance cues. Finally, we will determine whether the mechanism of action is an effect of anesthetics on GABAA receptors and/or NMDA receptors that leads to alterations in the levels and distribution of growth cone Ca2+, a principal intracellular regulator of the guidance response. (2) Determine whether effects of general anesthetics on axon guidance can lead to errors in circuit formation. The hypothesis to be tested is that anesthetic agents can disrupt axon targeting, thus leading to errors in circuit formation. The trajectory of axons in an organotypic slice culture model of axon guidance that is exposed to anesthetics will be assessed for errors in development to determine which agents may have deleterious effects. Subsequently, the development of the mossy fibers and the Schaffer collaterals, two tracts of the hippocampus that participate in a critical learning circuit, will be assessed after anesthetic exposure to determine which agents, what doses, and what exposure times can disrupt circuit formation. These studies will take place in organotypic brain slice culture using quantitative microscopy and electrophysiologic techniques. Results will be confirmed by microscopic analysis of these tracts in intact mice exposed to the anesthetic agents determined in slice culture to interfere with axon guidance and tract formation.

描述（由申请人提供）：流行病学研究表明，儿童期暴露于麻醉与随后的学习和行为障碍之间存在联系。这些数据得到了动物研究的补充，表明暴露于麻醉药的大鼠幼崽在学习中表现出持久的缺陷。先前的研究人员表明，麻醉剂可以增加发育中的大脑的凋亡，但是几乎没有用来评估麻醉药对剩余神经元发展的影响。我们的初步数据引起了人们的关注，即在临床上相关剂量上提出的一些通常使用的麻醉药可能会干扰轴突生长锥对指导它们的提示的反应，从而导致它们对正确的树突状靶标的提示，从而破坏了对较高功能的Brai电路的形成，例如学习。在此提案中，我们将检查麻醉剂对轴突指导和电路形成的主要类别，以发现发现这种有害效果的机制，并确定如何设计麻醉计划以避免或最小化。具体目的是：（1）测试一般麻醉剂对轴突生长锥对引导提示的反应的影响。要测试的假设是，具有GABAA受体和/或NMDA受体活性的麻醉剂可以实质上干扰生长锥功能，包括感应和对引导提示的反应。使用延时显微镜和轴突形态的定量分析，我们将在没有指导线索的情况下确定主要类麻醉剂对轴突生长锥运动的影响。然后，使用塌陷测定法和梯度转弯测定法，我们将测试麻醉药是否干扰轴突生长锥对排斥和有吸引力的引导提示的反应。最后，我们将确定作用机理是否是麻醉剂对GABAA受体和/或NMDA受体的影响，后者导致生长锥Ca2+的水平和分布改变，这是指导反应的主要细胞内调节剂。 （2）确定一般麻醉药对轴突指导的影响是否会导致电路形成错误。要测试的假设是麻醉剂会破坏轴突的靶向，从而导致电路形成错误。轴突引导的器官切片培养模型中轴突暴露于麻醉剂的轨迹将被评估出发育中的错误，以确定哪些药物可能具有有害作用。随后，苔藓纤维和沙弗侧支的开发，这是参与关键学习电路的海马的两个领域 麻醉暴露后评估以确定哪些药物，哪些剂量以及哪些暴露时间会破坏电路的形成。这些研究将使用定量显微镜和电生理技术在器官型脑切片培养中进行。通过微观分析对这些区域的微小分析，将证实结果，暴露于在切片培养中确定的麻醉剂，以干扰轴突引导和道的形成。