Jia X X, Gorczyca M, Budnik V
Department of Biology, University of Massachusetts at Amherst 01003.
J Neurobiol. 1993 Aug;24(8):1025-44. doi: 10.1002/neu.480240804.
The ventral longitudinal muscles of the Drosophila larval body wall are innervated by at least four types of synaptic terminals that can be distinguished on morphological grounds at the light microscopical level. The innervation of these muscles has been previously shown to be regulated by neuronal activity. In this report we investigate the ultrastructural basis for synaptic bouton differences by using serial sections, and examine the structure of synaptic terminals in mutants with increased excitability. We report that individual identifiable muscle fibers are innervated by terminals containing two to three types of synaptic boutons that can be distinguished in terms of synaptic vesicle population, presynaptic and postsynaptic specialization, and general shape. We propose a model to account for the bouton types observed at the light microscopical level. We find that in the hyperexcitable mutant eag Sh, there are dramatic ultrastructural alterations at synaptic boutons. These alterations include a partial depletion of two types of synaptic vesicles and a change in appearance of a third type, changes in number and appearance of synaptic densities, and the presence of multivesicular bodies. Our results show that an increase in neuronal excitability produces profound effects in synaptic terminal structure.
果蝇幼虫体壁的腹侧纵肌由至少四种类型的突触终末支配，在光学显微镜水平上可根据形态学特征将它们区分开来。此前已表明，这些肌肉的神经支配受神经元活动的调节。在本报告中，我们使用连续切片研究突触小体差异的超微结构基础，并检查兴奋性增加的突变体中突触终末的结构。我们报告称，单个可识别的肌纤维由包含两到三种突触小体类型的终末支配，这些突触小体可根据突触小泡群体、突触前和突触后特化以及总体形状来区分。我们提出了一个模型来解释在光学显微镜水平上观察到的突触小体类型。我们发现，在兴奋性过高的突变体eag Sh中，突触小体存在显著的超微结构改变。这些改变包括两种突触小泡部分耗尽、第三种突触小泡外观改变、突触密度数量和外观变化以及多囊泡体的存在。我们的结果表明，神经元兴奋性增加会对突触终末结构产生深远影响。
