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，儿童期接触麻醉与随后学习和行为障碍的增加之间存在关联。这些数据得到了动物研究的补充，表明接触麻醉剂的幼鼠表现出持久的学习缺陷。先前的研究人员已经证明麻醉剂可以增加发育中大脑的细胞凋亡，但很少有人评估麻醉剂对剩余神经元发育的影响。我们的初步数据引起了人们的担忧，即一些临床相关剂量的常用麻醉剂可能会干扰轴突生长锥对引导其到达正确树突目标的线索的反应，从而可能破坏对高级功能至关重要的脑回路的形成，比如学习。在本提案中，我们将研究主要类别麻醉剂对轴突引导和回路形成的影响，以期发现这种有害影响的机制，并确定如何设计麻醉计划来避免或最小化它。具体目标是：（1）测试全身麻醉剂对轴突生长锥对引导信号的反应的影响。待测试的假设是，对 GABAA 受体和/或 NMDA 受体具有活性的麻醉剂可以显着干扰生长锥功能，包括对引导信号的感知和响应。使用延时显微镜和轴突形态的定量分析，我们将确定在没有引导线索的情况下主要类别的麻醉剂对轴突生长锥运动的影响。然后，使用塌陷测定和梯度转向测定，我们将测试麻醉剂是否干扰轴突生长锥对排斥和吸引引导线索的反应。最后，我们将确定作用机制是否是麻醉剂对 GABAA 受体和/或 NMDA 受体的影响，导致生长锥 Ca2+（指导反应的主要细胞内调节因子）水平和分布的改变。 (2) 确定全身麻醉对轴突引导的影响是否会导致回路形成错误。要测试的假设是麻醉剂可以破坏轴突靶向，从而导致回路形成错误。将评估暴露于麻醉剂的轴突引导的器官切片培养模型中的轴突轨迹是否存在发育错误，以确定哪些药剂可能具有有害作用。随后，苔藓纤维和谢弗络脉（参与关键学习回路的海马体的两个区域）的发育将受到影响。 麻醉暴露后进行评估，以确定哪些药物、剂量和暴露时间会破坏回路形成。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。结果将通过对暴露于切片培养物中确定的麻醉剂的完整小鼠中的这些纤维束进行显微分析来证实，以干扰轴突引导和纤维束形成。