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首页> 外文期刊>Journal of neurobiology >En passant synaptic varicosities form directly from growth cones by transient cessation of growth cone advance but not of actin-based motility.
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En passant synaptic varicosities form directly from growth cones by transient cessation of growth cone advance but not of actin-based motility.

机译：传代突触静脉曲张直接通过生长锥前进的暂时停止而从生长锥形成，而不是基于肌动蛋白的运动。

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摘要

Formation of terminal synapses at sites such as the neuromuscular junction involves transformation of the motile growth cone into the nonmotile synaptic terminal. However, transformation does not need to be the mechanism when a neurite forms multiple widely spaced synaptic varicosities along a target in an en passant configuration. Synaptic varicosities could form here by specialization of the neurite after the growth cone has advanced past the site. We examined this issue by using cocultures of identified sensory (SN) and motor (L7) neurons from Aplysia. Living SNs were labeled with fluorescent dye and their neurites were observed at high resolution every few minutes growing along the axon of L7, allowing a fine-grained analysis of the behavior of the growth cone at the sites of synapse formation. All varicosities whose formation was observed indeed developed from the growth cone. Sensory varicosities were shown by electron microscopy to contain features characteristic of active zones for transmitter release within a day of their formation on the motor axon. Growth cone advance slowed or stopped transiently during varicosity formation, but the motile activity of the peripheral region of the growth cone (veils and filopodia) was maintained. These results suggest that target "stop signals" involved in the formation of synapses, at least of the en passant variety, may be of a different type from the growth inhibitory molecules, such as the collapsins, which guide axons to their targets. Copyright 1999 John Wiley & Sons, Inc.
机译：在诸如神经肌肉接头的部位形成末端突触涉及将运动生长锥转化为非运动突触末端。但是，当神经突沿靶标以顺子构型形成多个间隔较宽的突触静脉曲张时，转变不一定是这种机制。在生长锥经过该部位后，通过神经突的特化可形成突触静脉曲张。我们通过使用来自Aplysia的已确定的感觉（SN）和运动（L7）神经元的共培养物研究了这个问题。活着的SN用荧光染料标记，沿着L7轴突每隔几分钟就可以高分辨率观察到它们的神经突，从而可以对突触形成部位生长锥的行为进行细粒度分析。观察到其形成的所有静脉曲张的确从生长锥发育而来。电子显微镜显示感觉静脉曲张包含活动区的特征，该活动区在发送者在运动轴突上形成后的一天之内释放。在静脉曲张形成过程中，生长锥的前进速度变慢或停止，但是保持了生长锥外围区域（面纱和丝状伪足）的活动能力。这些结果表明，参与突触形成的靶标“终止信号”，至少是整个传代品种，可能与将轴突导向其靶标的生长抑制分子（例如胶原蛋白）的类型不同。版权所有1999 John Wiley＆Sons，Inc.

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