Brandstätter J H, Shaw S R, Meinertzhagen I A
Life Sciences Centre, Dalhousie University, Halifax, Nova Scotia, Canada.
Proc Biol Sci. 1992 Jan 22;247(1318):1-7. doi: 10.1098/rspb.1992.0001.
Following photo-ablation of receptor cells in the retina of the housefly's compound eye, their synaptic terminals degenerate with a timecourse which we have followed over 8 d. Degeneration deprives the monopolar interneurons in the first optic neuropile, the lamina, of their main synaptic input. Simultaneously it deprives one monopolar interneuron (L2) of one of its synaptic targets, as L2 makes numerous feedback synaptic contacts at which it is pre-synaptic upon receptor terminals. Because the feedback synapses are dyadic, input still remains available to the second element post-synaptic at the dyad, which does not degenerate. This element is T1, a higher-order interneuron from the next most proximal neuropile (the medulla). Some of the original feedback synaptic sites soon disappear as a consequence of the photo-ablation, but their loss is partly offset by the production of new synaptic contacts. The new pre-synaptic ribbons resemble those at the original sites except for being smaller. The sites are, moreover, monadic, with T1 now the sole post-synaptic partner. These results show that interneurons in the fly's lamina retain a dynamic capacity for synaptogenesis throughout much of adult life, normally a few weeks in Musca, and that during this synaptogenesis they re-enact the same cell preferences expressed earlier in development.
在家蝇复眼视网膜中的受体细胞经光消融后，其突触终末会在8天的时间进程中发生退化。退化过程使第一视觉神经节层中的单极中间神经元失去了主要的突触输入。同时，它也使一个单极中间神经元（L2）失去了其一个突触靶点，因为L2会在受体终末上形成众多反馈突触联系，在这些联系中L2是突触前成分。由于反馈突触是二元的，对于二元突触中突触后第二个成分来说，输入仍然可用，该成分不会退化。这个成分是T1，它是来自下一个最靠近近端的神经节（髓质）的高阶中间神经元。光消融导致一些原始反馈突触位点很快消失，但新突触联系的产生部分抵消了它们的损失。新的突触前带与原始位点的相似，只是尺寸较小。此外，这些位点是单元的，现在T1是唯一的突触后伙伴。这些结果表明，果蝇层中的中间神经元在成年后的大部分时间里都保留着突触形成的动态能力，在家蝇中通常是几周时间，并且在这种突触形成过程中，它们再次表现出在发育早期所表达的相同细胞偏好。
