Regulation of synaptic frequency: comparison of the effects of hypoinnervation with those of hyperinnervation in the fly's compound eye.
Regulation of synaptic frequency: comparison of the effects of hypoinnervation with those of hyperinnervation in the fly's compound eye.
复制标题
突触频率的调节：果蝇复眼中神经支配不足与神经支配过度的影响的比较。
DOI：
10.1002/neu.480180403
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发表时间：
1987
期刊：
影响因子：
--
通讯作者：
Meinertzhagen,IA
中科院分区：
文献类型：
--
作者：
Fröhlich,A;Meinertzhagen,IA
在家蝇复眼的第一视神经丛或层的前缘，光感受器（R）的末梢以可变数量支配突触后神经元，以提供连续范围的天然神经支配不足和过度。光感受器突触的频率已经通过定量电子显微镜在被称为盒的单层单位突触模块的单个切片上测量。这些通常由六个感光末梢（6 R盒）支配。在椎板的边缘发现了神经支配不足的盒（2 R-5 R），而神经支配过度的盒（7 R，8 R）位于背侧和腹侧眼半之间的赤道处。在2 R盒中，每个突触前末端形成的突触数量是正常的6 R盒数量的1.5倍，从而抵消了减少的末端数量，并部分保留了突触后神经元的输入。因此，终端有一个储备突触的能力从来没有正常显示。相比之下，8 R盒中的末端形成的突触数量与“正常”眼区中的突触数量大致相同，因此它们的突触后神经元具有因额外数量的末端而增加的突触输入。因此，在输入终末和靶神经元之间形成的突触的数量不是固定的，而是作为总受体终末补体的函数而变化。光感受器末梢的大小在一定程度上与其突触前位点的数量相关;与8 R盒相比，2 R盒中末梢表面上突触前位点的间距密度的增加（仅17%）远小于位点数量的增加（43%）。与8 R盒中的那些相比，每个2 R盒中的突触后细胞中间神经元对也显示出轴突直径的减小。因此，突触前和突触后细胞都显示出与其突触接合变化相关的大小变化。
At the anterior rim of the first optic neuropile, or lamina, of the housefly's (Musca domestica) compound eye, the terminals of photoreceptors (R) innervate postsynaptic neurons in variable numbers to provide a continuous range of natural hypo‐and hyperinnervations. Frequencies of photoreceptor synapses have been measured from quantitative electron microscopy on single sections of the lamina's unit synaptic modules, called cartridges. These are normally innervated by six photoreceptor terminals (6R cartridges). At the lamina's edge hypoinnervated cartridges (2R–5R) are found, whereas hyperinnervated cartridges (7R, 8R) are located at the equator between dorsal and ventral eye halves. In 2R cartridges each presynaptic terminal forms up to 1.5 times the normal, 6R cartridge number of synapses, thereby offsetting the reduced number of terminals and partially conserving the input upon the postsynaptic neurons. Thus the terminals have a reserve synaptogenic capacity never normally revealed. By comparison, terminals in 8R cartridges form about the same numbers of synapses as in “normal” eye regions, so that their postsynaptic neurons have a synaptic input increased by the extra number of terminals. The number of synapses formed between input terminals and target neurons is therefore not fixed but changes as a function of the total receptor terminal complement. The size of a photoreceptor terminal covaries to a certain extent with the number of its presynaptic sites; the spacing density of presynaptic sites over the terminals' surface in a 2R cartridge compared with an 8R cartridge increases far less (only 17%) than the increase in the number of sites (43%). The pair of postsynaptic cell interneurons in each 2R cartridge also shows a decrease in axonal diameter compared with those in 8R cartridges. Thus both the pre‐ and postsynaptic cells show size changes correlated with changes in their synaptic engagement.