Morphological changes in the neuritic growth cone and target neuron during synaptic junction development in culture
Morphological changes in the neuritic growth cone and target neuron during synaptic junction development in culture
复制标题
培养中突触连接发育过程中神经炎生长锥和靶神经元的形态变化
作者：
R. Rees;M. Bunge;R. Bunge
我们的目的是描述突触前和突触后元件在最初接触和随后成熟为典型突触轮廓期间发生的形态变化。来自围产期大鼠颈上神经节（SCG）的神经元被去除其支持细胞，并在培养物中建立为分离的细胞。向其中添加胚胎大鼠胸脊髓的外植体，以允许向外生长的脊髓神经突和分离的自主神经元之间相互作用。通过光学显微镜评估初始接触时间；此后每隔一段时间固定培养物用于电子显微镜检查。接触后，生长锥丝状伪足广泛应用于 SCG 神经元质膜，并表现出许多点状区域，其中相邻的质膜仅相隔 7-10 nm。目标神经元的高尔基体肥大，其包被囊泡的产生增加。在紧密接触部位附近观察到与 SCG 质膜连续的类似囊泡；它们对具有底涂层的突触后膜区域的明显贡献被认为是突触形成的第一个明确标志。过氧化物酶和铁蛋白的示踪工作证实，神经元体细胞内包被囊泡的运输主要是从高尔基体区域到体细胞表面。突触后密度出现后，生长锥的形式和内容因丝状伪足的丧失和突触小泡的出现而改变，突触小泡逐渐聚集在突触后密度对面。随着突触的成熟，突触小泡数量增多，裂隙宽度和含量增加，突触前密度出现，分支膜网大大减少，大部分溶酶体结构消失。在成熟的所有阶段，包被的囊泡继续与突触后膜相关。将高尔基体衍生的囊泡掺入细胞膜的离散区域可以提供将神经元膜的特定特征限制在突触区域的机制。
Our object was to characterize the morphological changes occurring in pre- and postsynaptic elements during their initial contact and subsequent maturation into typical synaptic profiles. Neurons from superior cervical ganglia (SCG) of perinatal rats were freed of their supporting cells and established as isolated cells in culture. To these were added explants of embryonic rat thoracic spinal cord to allow interaction between outgrowing cord neurites and the isolated autonomic neurons. Time of initial contact was assessed by light microscopy; at timed intervals thereafter, cultures were fixed for electron microscopy. Upon contact, growth cone filopodia became extensively applied to the SCG neuronal plasmalemma and manifested numerous punctate regions in which the apposing plasma membranes were separated by only 7-10 nm. The Golgi apparatus of the target neuron hypertrophied, and its production of coated vesicles increased. Similar vesicles were seen in continuity with the SCG plasmalemma near the close contact site; their apparent contribution of a region of postsynaptic membrane with undercoating was considered to be the first definitive sign of synapse formation. Tracer work with peroxidase and ferritin confirmed that the traffic of coated vesicles within the neuronal soma is largely from Golgi region to somal surface. Subsequent to the appearance of postsynaptic density, the form and content of the growth cone was altered by the loss of filopodia and the appearance of synaptic vesicles which gradually became clustered opposite the postsynaptic density. As the synapse matured, synaptic vesicles increased in number, cleft width and content increased, presynaptic density appeared, branched membranous reticulum became greatly diminished, and most lysosomal structures disappeared. Coated vesicles continued to be associated with the postsynaptic membrane at all stages of maturation. The incorporation of Golgi-derived vesicles into discrete regions of the cell membrane could provide the mechanism for confining specific characteristics of the neuronal membrane to the synaptic region.