Rollenhagen Astrid, Sadeghi Akram, Walkenfort Bernd, Hilgetag Claus C, Sätzler Kurt, Lübke Joachim H R
Institute of Neuroscience and Medicine INM-10, Research Centre Jülich GmbH, Jülich, Germany.
Medical Research Centre, IMCES Electron Microscopy Unit (EMU), University Hospital Essen, Essen, Germany.
Elife. 2025 Jul 21;13:RP99473. doi: 10.7554/eLife.99473.
Layer (L)1, beside receiving massive cortico-cortical, commissural and associational projections, is the termination zone of tufted dendrites of pyramidal neurons and the area of Ca spike initiation. However, its synaptic organization in humans is not known. Quantitative 3D models of excitatory synaptic boutons (SBs) in L1 of the human temporal lobe neocortex were generated from neocortical biopsy tissue using transmission electron microscopy, 3D-volume reconstructions, and TEM tomography. Particularly, the size of active zones (AZs) and the readily releasable, recycling, and resting pool of synaptic vesicles (SVs) were quantified. The majority of excitatory SBs contained numerous mitochondria comprising 7% of the total volume, had a large macular, non-perforated AZ (0.20 µm) and were predominantly located on dendritic spines. Excitatory SBs had a total pool of 3500 SVs, a relatively large readily releasable (4 SVs), recycling (470 SVs) and resting (2900 SVs) pool. Astrocytic coverage of excitatory SBs suggests both synaptic crosstalk or removal of spilled glutamate by astrocytic processes at synaptic complexes. The structural composition of SBs in L1 may underlie the function of L1 networks that mediate, integrate, and synchronize contextual and cross-modal information, enabling flexible and state-dependent processing of feedforward sensory inputs from other layers of the cortical column.
第1层（L1）除了接收大量皮质-皮质、连合和联合投射外，还是锥体神经元簇状树突的终末区和钙峰起始区域。然而，其在人类中的突触组织尚不清楚。利用透射电子显微镜、三维体积重建和透射电镜断层扫描技术，从新皮质活检组织中生成了人类颞叶新皮质L1中兴奋性突触小体（SBs）的定量三维模型。特别地，对活性区（AZs）的大小以及突触囊泡（SVs）的易释放池、循环池和静息池进行了定量。大多数兴奋性SBs含有大量线粒体，占总体积的7%左右，具有一个大的黄斑、无穿孔的活性区（约0.20 µm），主要位于树突棘上。兴奋性SBs共有约3500个突触囊泡，其中易释放池相对较大（约4个突触囊泡），循环池（约470个突触囊泡）和静息池（约2900个突触囊泡）。星形胶质细胞对兴奋性SBs的覆盖表明，在突触复合体处，星形胶质细胞过程可实现突触间串扰或清除溢出的谷氨酸。L1中SBs的结构组成可能是L1网络功能的基础，该网络介导、整合和同步上下文及跨模态信息，从而能够对来自皮质柱其他层的前馈感觉输入进行灵活的、状态依赖的处理。
