The effects of anesthetics on brain development

麻醉药对大脑发育的影响

• 批准号: 8424885
• 负责人: Cyrus David Mintz
• 金额: $ 4.8万
• 依托单位: COLUMBIA UNIVERSITY HEALTH SCIENCES
• 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 2013-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8424885
• 关键词: Acids; Anesthesia procedures; Anesthetics; Animals; Apoptosis; Axon; Behavior Disorders; Biological Assay; Brain; Child; Childhood; Complement; Complex; Cues; Data; Defect; Dependence; Development; Developmental Process; Dose; Electrophysiology (science); Epidemiologic Studies; Exhibits; Exposure to; General anesthetic drugs; Growth Cones; Hippocampal Formation; Hippocampus (Brain); Human; Isoflurane; Lead; Learning; Learning Disabilities; Learning Disorders; Life; Locomotion; Measures; Mediating; Medical; Memory; Microscopic; Microscopy; Modeling; Morphology; Mus; N-Methyl-D-Aspartate Receptors; Neurons; Operative Surgical Procedures; Pattern; Play; Process; Property; Quantitative Microscopy; Rattus; Regulation; Research Personnel; Role; Semaphorin-3A; Shapes; Slice; Synapses; Techniques; Testing; Time; United States; axon growth; axon guidance; base; brain cell; cell motility; clinically relevant; clinically significant; design; mossy fiber; mouse model; neocortical; neuron development; public health relevance; pup; receptor; receptor function; response; small hairpin RNA; time use

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，儿童暴露于麻醉与随后的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，表明暴露于麻醉剂的大鼠幼崽在学习方面表现出持久的缺陷。先前的研究人员已经证明，麻醉剂可以增加发育中的大脑细胞凋亡，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关注，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它们到达正确树突目标的信号的反应，从而潜在地破坏对高级功能（如学习）至关重要的大脑回路的形成。在本提案中，我们将研究主要类别的麻醉剂对轴突引导和电路形成的影响，以期发现这种有害影响的机制，并确定如何设计麻醉方案以避免或最小化它。具体目的是：(1)测试全麻药物对轴突生长锥对引导信号反应的影响。需要验证的假设是，具有GABAA受体和/或NMDA受体活性的麻醉剂可以实质性地干扰生长锥的功能，包括对引导信号的感知和反应。利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，主要种类的麻醉剂对轴突生长锥体运动的影响。然后，使用塌陷实验和梯度转向实验，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信号的反应。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+水平和分布的改变，Ca2+是指导反应的主要细胞内调节剂。(2)确定全麻对轴突引导的影响是否会导致电路形成错误。要测试的假设是，麻醉剂可以破坏轴突的靶向，从而导致电路形成错误。在暴露于麻醉药的轴突引导的器官型切片培养模型中，轴突的轨迹将被评估以确定哪些药物可能具有有害影响。随后，海马体中参与关键学习回路的两个束——苔藓纤维和Schaffer侧枝的发育将被切断