Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA.
Neuron. 2010 Sep 23;67(6):1009-20. doi: 10.1016/j.neuron.2010.08.014.
Complete reconstructions of vertebrate neuronal circuits on the synaptic level require new approaches. Here, serial section transmission electron microscopy was automated to densely reconstruct four volumes, totaling 670 μm(3), from the rat hippocampus as proving grounds to determine when axo-dendritic proximities predict synapses. First, in contrast with Peters' rule, the density of axons within reach of dendritic spines did not predict synaptic density along dendrites because the fraction of axons making synapses was variable. Second, an axo-dendritic touch did not predict a synapse; nevertheless, the density of synapses along a hippocampal dendrite appeared to be a universal fraction, 0.2, of the density of touches. Finally, the largest touch between an axonal bouton and spine indicated the site of actual synapses with about 80% precision but would miss about half of all synapses. Thus, it will be difficult to predict synaptic connectivity using data sets missing ultrastructural details that distinguish between axo-dendritic touches and bona fide synapses.
完整重建脊椎动物神经元回路的突触水平需要新的方法。在这里，我们采用自动化串行切片透射电子显微镜技术，从大鼠海马体中重建了四个体积，总共 670 μm(3)，作为确定轴突-树突接近程度是否能预测突触的试验场。首先，与彼得斯定律相反，树突棘可触及范围内的轴突密度并不能预测树突上的突触密度，因为形成突触的轴突比例是可变的。其次，轴突-树突接触并不预示着有突触；然而，海马树突上的突触密度似乎是接触密度的一个普遍分数，约为 0.2。最后，轴突末梢和棘突之间最大的接触预示着实际突触的位置，准确率约为 80%，但会错过大约一半的突触。因此，使用缺少区分轴突-树突接触和真正突触的超微结构细节的数据来预测突触连接将是困难的。
