Schuster Christoph M
Interdisciplinary Center for Neurosciences (ICN), Department of Neurobiology, University of Heidelberg, 69120 Heidelberg, Germany.
Cell Tissue Res. 2006 Nov;326(2):287-99. doi: 10.1007/s00441-006-0290-5. Epub 2006 Aug 1.
The glutamatergic synapses of developing neuromuscular junctions (NMJ) of Drosophila larvae are readily accessible, morphologically simple, and physiologically well-characterized. They therefore have a long and highly successful tradition as a model system for the discovery of genetic and molecular mechanisms of target recognition, synaptogenesis, NMJ development, and synaptic plasticity. However, since the development and the activity-dependent refinement of NMJs are concurrent processes, they cannot easily be separated by the widely applied genetic manipulations that mostly have chronic effects. Recent studies have therefore begun systematically to incorporate larval foraging behavior into the physiological and genetic analysis of NMJ function in order to analyze potential experience-dependent changes of glutamatergic transmission. These studies have revealed that recent crawling experience is a potent modulator of glutamatergic transmission at NMJs, because high crawling activities result after an initial lag-phase in several subsequent phases of experience-dependent synaptic potentiation. Depending on the time window of occurrence, four distinct phases of experience-dependent potentiation have been defined. These phases of potentiation can be followed from their initial induction (phase-I) up to the morphological consolidation (phase-III/IV) of previously established functional changes (phase-II). This therefore establishes, for the first time, a temporal hierarchy of mechanisms involved in the use-dependent modification of glutamatergic synapses.
果蝇幼虫发育中的神经肌肉接头（NMJ）的谷氨酸能突触易于接近，形态简单，生理特征明确。因此，作为发现靶标识别、突触形成、NMJ发育和突触可塑性的遗传和分子机制的模型系统，它们有着悠久且极为成功的传统。然而，由于NMJ的发育和依赖活动的精细化是并行过程，它们难以通过大多具有慢性影响的广泛应用的基因操作轻易分离。因此，最近的研究开始系统地将幼虫觅食行为纳入NMJ功能的生理和遗传分析中，以分析谷氨酸能传递中潜在的经验依赖性变化。这些研究表明，最近的爬行经历是NMJ处谷氨酸能传递的有力调节因子，因为在最初的滞后阶段后，高爬行活动会在随后几个经验依赖性突触增强阶段出现。根据发生的时间窗口，已定义了经验依赖性增强的四个不同阶段。这些增强阶段可以从其最初诱导（I期）一直追踪到先前建立的功能变化（II期）的形态巩固（III/IV期）。因此，这首次确立了参与谷氨酸能突触使用依赖性修饰的机制的时间层次结构。
