Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, 1432 As, Norway.
J Comp Neurol. 2010 Aug 1;518(15):2903-16. doi: 10.1002/cne.22396.
Nitric oxide (NO) is an evolutionarily conserved mediator of neural plasticity. Because NO is highly diffusible, signals from multiple sources might combine in space and time to affect the same target. Whether such cooperative effects occur will depend on the effective signaling range and on the distances of NO sources to one another and to their targets. These anatomical parameters have been quantified in only few systems. We analyzed the 3D architecture of NO synthase (NOS) expression in a sensory neuropil, the ventral association center (VAC) of the locust. High-resolution confocal microscopy revealed NOS immunoreactive fiber boutons in submicrometer proximity to both the axon terminals of sensory neurons and their postsynaptic target, interneuron A4I1. Pharmacological manipulation of NO signaling affected the response of A4I1 to individual wind-puff stimuli and the response decrement during repetitive stimulation. Mapping NOS immunoreactivity in defined volumes around dendrites of A4I1 revealed NOS-positive fiber boutons within 5 mum of nearly every surface point. The mean distances between neighboring NOS-boutons and between any point within the VAC and its nearest NOS-bouton were likewise about 5 mum. For an NO signal to convey the identity of its source, the effective signaling range would therefore have to be less than 5 mum, and shorter still when multiple boutons release NO simultaneously. The architecture is therefore well suited to support the cooperative generation of volume signals by interaction between the signals from multiple active boutons.
一氧化氮（NO）是一种进化上保守的神经可塑性介质。由于 NO 具有高度的扩散性，来自多个来源的信号可能会在空间和时间上结合，从而影响同一目标。这种协同效应是否会发生将取决于有效信号范围，以及 NO 源与彼此以及与目标之间的距离。这些解剖学参数仅在少数系统中进行了量化。我们分析了位于蝗虫感觉神经纤维球（VAC）腹侧联合中心（VAC）中的一氧化氮合酶（NOS）表达的 3D 结构。高分辨率共聚焦显微镜显示，NOS 免疫反应性纤维末梢在亚微米距离内与感觉神经元的轴突末梢及其突触后靶标，中间神经元 A4I1 接近。NO 信号转导的药理学操纵影响 A4I1 对单个风刺激的反应以及重复刺激期间的反应衰减。在 A4I1 树突周围的特定体积中绘制 NOS 免疫反应性显示，在近每一个表面点都有 NOS 阳性纤维末梢。相邻 NOS 末梢之间以及 VAC 内的任何点与其最近的 NOS 末梢之间的平均距离也约为 5 µm。为了使 NO 信号传递其来源的身份，有效信号范围必须小于 5 µm，而当多个末梢同时释放 NO 时，信号范围会更短。因此，该结构非常适合通过来自多个活跃末梢的信号之间的相互作用来支持体积信号的协同产生。
