Three-Dimensional Reconstruction of a Calyx of Held and Its Postsynaptic Principal Neuron in the Medial Nucleus of the Trapezoid Body
Three-Dimensional Reconstruction of a Calyx of Held and Its Postsynaptic Principal Neuron in the Medial Nucleus of the Trapezoid Body
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DOI：
10.1523/jneurosci.22-24-10567.2002
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发表时间：
2002-12
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通讯作者：
K. Sätzler;K. Sätzler;Leander F Söhl;Johann H. Bollmann;J. Borst;M. Frotscher;B. Sakmann;J. Lübke
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作者：
K. Sätzler;K. Sätzler;Leander F Söhl;Johann H. Bollmann;J. Borst;M. Frotscher;B. Sakmann;J. Lübke
用连续切片重建了出生后9天大鼠脑干Held萼与斜方体内侧核（MNTB）主神经元之间轴体突触结构的三维形态。在肾盏和主神经元之间的贴壁区，两种类型的膜特化被确定：突触接触（SC）与活动区（AZ）和其相关的突触后密度（PSD）构成的专业化的约35%（n = 554），其余65%（n = 1010）的点adherentia（PA）。突触接触占突触前膜和突触后膜贴壁面积的0.5%。SC的平均面积为0.100 μm2，最近的邻居平均分开0.59 μm。大约有一半的突触囊泡在花萼聚集在AZ膜区域的200 nm的距离内，一个由大约60个突触囊泡组成的簇（n = 52个SC）。每个SC大约有两个突触囊泡“解剖对接”。将突触结构的几何形状与其先前研究的功能特性进行比较，我们发现在单个突触前动作电位（AP）期间，（1）大约35%的AZ释放一个递质量子，（2）SC和解剖学对接的囊泡的数量与量子的易释放池（RRP）的低估计值相当，（3）PSD面积的广泛分布[变异系数（CV）= 0.9]可能导致微型EPSC峰的大变异性。重建突触的几何形状表明，在单个AP期间，数百个SC中的每一个都可能独立地对EPSC的大小和上升相位做出贡献。
The three-dimensional morphology of the axosomatic synaptic structures between a calyx of Held and a principal neuron in the medial nucleus of the trapezoid body (MNTB) in the brainstem of young postnatal day 9 rats was reconstructed from serial ultrathin sections. In the apposition zone between the calyx and the principal neuron two types of membrane specializations were identified: synaptic contacts (SCs) with active zones (AZs) and their associated postsynaptic densities (PSDs) constituted ∼35% (n = 554) of the specializations; the remaining 65% (n = 1010) were puncta adherentia (PA). Synaptic contacts comprised ∼5% of the apposition area of presynaptic and postsynaptic membranes. A SC had an average area of 0.100 μm2, and the nearest neighbors were separated, on average, by 0.59 μm. Approximately one-half of the synaptic vesicles in the calyx were clustered within a distance of 200 nm of the AZ membrane area, a cluster consisting of ∼60 synaptic vesicles (n = 52 SCs). Approximately two synaptic vesicles per SC were “anatomically docked.” Comparing the geometry of the synaptic structure with its previously studied functional properties, we find that during a single presynaptic action potential (AP) (1) ∼35% of the AZs release a transmitter quantum, (2) the number of SCs and anatomically docked vesicles is comparable with the low estimates of the readily releasable pool (RRP) of quanta, and (3) the broad distribution of PSD areas [coefficient of variation (CV) = 0.9] is likely to contribute to the large variability of miniature EPSC peaks. The geometry of the reconstructed synapse suggests that each of the hundreds of SCs is likely to contribute independently to the size and rising phase of the EPSC during a single AP.