Estructuras Subcelulares en Sinapsis Hipocampales Nativas Reveladas por Criotomografía Electrónica

Synapses, the core components of neuronal circuits, rely on precise ultrastructural and molecular organization to facilitate quantal transmission and plasticity, which underpin brain information processing and storage. Cryo-electron tomography (cryo-ET) has emerged as a powerful tool for elucidating the nanoscale architecture of synapses, yet prior studies have largely focused on synaptic vesicles and postsynaptic receptors, leaving other critical components underexplored. Here, we employed cryo-ET to quantitatively analyze subcellular features across over 300 intact hippocampal synapses, revealing: (1) A significant proportion of excitatory synapses (32%) localized to dendritic shafts, while a relatively high proportion of inhibitory synapses targeted dendritic spines (35%), with synaptic clefts displaying four distinct geometries; (2) Diverse structures, including dense core vesicles, membraneless dense granules, and empty clathrin cages were enriched within presynaptic boutons; (3) Mitochondria prevalent in both pre- and postsynaptic regions, showing higher abundance of mitochondrial matrix granules postsynaptically. These findings provide a comprehensive view of the structural organization within hippocampal synapses and suggest fundamental principles governing their subcellular architecture.