COMPETITION BETWEEN AXONS AT THE NEUROMUSCULAR JUNCTION

一些证据表明， 突触后细胞上的轴突接触受到竞争性 轴突之间的相互作用。 的目的是为了更好地 了解规范这种竞争的发展战略。 这些研究将利用几种新开发的技术， 活体标本中突触末梢在光照下的可视化 显微镜 轴突数量的正常竞争性减少， 神经支配突触后细胞之后，将观察 不同的轴突以一种新的方式通过依赖于活动的示踪剂可见 摄取。 在存在以下任一种情况下运动轴突的短暂激活： 几种不同颜色的荧光分子选择性地填充 轴突突触末梢与示踪剂。 通过刺激不同的 轴突在不同颜色的探针的存在下，精确的分布 不同轴突的突触末梢的形状可以被描述。 这个简单 强大的技术将被用来描述正常发生的 神经支配肌肉纤维的轴突数量的竞争性减少 在蛇类和哺乳动物身上都有。 第二个目标是从解剖学和电生理学上研究 与突触重塑发生时相同的神经末梢。 以前未使用的荧光探针选择性染色的发现 哺乳动物运动神经末梢，几乎没有毒性， 低背景首次允许多个视图相同 哺乳动物的连接处。 这种荧光分子 将被用于监测突触连接的重组， 活小鼠在肌肉过程中的单个哺乳动物神经肌肉接头 神经再生 在活体终端研究突触竞争将 提供有关突触的动态方面的直接信息， 重塑--这是一个人们知之甚少的话题， 神经系统中一些最重要的长期变化的基础 系统（例如，学习和记忆）。

Several lines of evidence indicate that the number and distribution of axonal contacts on postsynaptic cells are regulated by competitive interactions between axons duuring development. The aim of is to better understand the developmental strategies that regulate this competition. The studies will utilize several newly developed techniques for the visualization of synaptic terminals in living preparations under the light microscope. The normally occurring competitive reduction in the number of axons that innervate a postsynaptic cell will be followed by viewing the terminals of different axons made visible in a novel way by activity dependent tracer uptake. Brief activation of a motor axon in the presence of any one of several differently colored fluorescent molecules selectively fills the synaptic terminals of that axon with the tracer. By stimulating different axons in the presence of different colored probes, the precise distribution of the synaptic terminals of different axons can be described. This simple and powerful technique will be used to characterize the normally occurring competitive reduction in the number of axons that innervate a muscle fiber in both snakes and mammals. The second goal is to study anatomically and electrophysiologically the same nerve terminals over time as synaptic remodelling is taking place. The finding that a previously unused fluorescent probe selectively stains mammalian motor nerve terminals with virtually no toxicity and extremely low background has for the first time permitted multiple views of the same mammalian junctions at different time points. This fluorescent molecule will be used to monitor the reorganization of synaptic connections at individual mammalian neuromuscular junctions in living mice during muscle reinnervation. Studying synaptic competition at living terminals will provide direct information about the dynamic aspects of synaptic remodelling -- a subject which is very poorly understood and presumably is the basis of some of the most important long-term changes in the nervous system (e.g., learning and memory).