Kruger Lawrence, Light Alan R, Schweizer Felix E
Department of Neurobiology and Brain Research Institute, Geffen School of Medicine, UCLA Medical Center, Los Angeles, CA 90951, USA.
J Neurocytol. 2003 Mar;32(3):205-16. doi: 10.1023/B:NEUR.0000010080.62031.f0.
The application of electron microscopy to defining the fine structural characteristics of axon terminals and synapses was followed by a half century of intensive exploration of the molecular concomitants of synaptic activity. The summer of 2003 marks the 50th anniversary of the earliest accounts of synapses by Palay and Palade. Prompted by recent findings of specialization in the fine structure of nociceptor terminals that lack contacts remotely resembling a synapse, we present a survey of arrangements, contacts and axoplasmic contents of peripheral sensory axon terminals. The morphological principles underlying the variety of small, clear, spherical vesicles, mitochondrial aggregation, the membrane thickenings associated with sensory terminals and the organelles or inclusions associated with the site of transduction apparently do not conform to a simple parsimonious rule. It is also evident that the terminal of the central branch of bifurcated sensory axons differs structurally from its distal counterparts. This brief illustrated account addresses some important unresolved problems in the functional interpretation of the diverse morphological features exhibited in both synaptic and non-synaptic sensory axon terminals with the aim of identifying and emphasizing some key questions amenable to resolution with contemporary morphological and physiological techniques.
在将电子显微镜应用于确定轴突终末和突触的精细结构特征之后，紧接着是对突触活动分子伴随物的半个世纪的深入探索。2003年夏天标志着帕莱和帕拉德最早描述突触的50周年。受最近关于伤害感受器终末精细结构特化的发现的启发，这些终末缺乏类似于突触的远距离接触，我们对周围感觉轴突终末的排列、接触和轴浆内容物进行了综述。各种小的、清亮的球形囊泡、线粒体聚集、与感觉终末相关的膜增厚以及与转导部位相关的细胞器或内含物所依据的形态学原理显然不符合一个简单的简约规则。同样明显的是，分叉感觉轴突中央支的终末在结构上与其远端对应物不同。这个配有插图的简要叙述探讨了在突触性和非突触性感觉轴突终末所表现出的各种形态特征的功能解释中一些重要的未解决问题，目的是识别并强调一些可用当代形态学和生理学技术解决的关键问题。
