Meinertzhagen I A
Life Sciences Centre, Dalhousie University, Halifax, Nova Scotia, Canada.
J Neurobiol. 1989 Jul;20(5):276-94. doi: 10.1002/neu.480200503.
Recent studies are reviewed on the synapses of photoreceptor terminals in the first optic neuropile of the flies, Musca and Drosophila. Afferent synaptic contacts are of uniform dimensions; they have a postsynaptic tetrad with a membrane organization of P-face particles, resembling other inhibitory synapses. A distributed population of such contact sites forms progressively during synaptogenesis by the selective, sequential accretion of identified postsynaptic elements at the receptor terminal. The comparative anatomy of this synapse indicates that elements have also been added during its phylogeny from an ancestral dyad. All cells are homologs of those in other species of Diptera. The number of synaptic sites is regulated by both pre- and postsynaptic cells, in proportion to their cell surfaces; an independent size increase in the receptor terminals (procured in the Drosophila mutant gigas) produces an increase in their synaptic population. The number of sites declines with age, however, accompanied by an increase in size of those synaptic sites remaining; this occurs for both afferent and feedback photoreceptor synapses. Lastly, the number of sites changes with visual experience; the frequency of feedback synapses is larger following dark rearing during early adult life than following visual experience.
本文综述了近期关于家蝇和果蝇第一视神经节中光感受器终末突触的研究。传入性突触接触具有统一的尺寸；它们有一个带有P面颗粒膜组织的突触后四联，类似于其他抑制性突触。在突触形成过程中，通过在受体终末选择性、顺序性地积累已确定的突触后元件，逐渐形成了这样一个分布式的接触位点群体。这种突触的比较解剖学表明，在其从祖先二元体进化的过程中也添加了一些元件。所有细胞都与双翅目其他物种中的细胞同源。突触位点的数量由突触前和突触后细胞共同调节，与它们的细胞表面积成比例；受体终末的独立尺寸增加（在果蝇突变体gigas中获得）会导致其突触群体增加。然而，随着年龄的增长，突触位点的数量会减少，同时剩余突触位点的尺寸会增加；这在传入性和反馈性光感受器突触中都会发生。最后，突触位点的数量会随着视觉经验而变化；在成年早期进行暗饲养后，反馈性突触的频率比有视觉经验后更高。
