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@ARTICLE{Rollenhagen:172036,
      author       = {Rollenhagen, Astrid and Klook, Kerstin and Sätzler, Kurt
                      and Qi, Guanxiao and Anstötz, Max and Feldmeyer, Dirk and
                      Lübke, Joachim},
      title        = {{S}tructural determinants underlying the high efficacy of
                      synaptic transmission and plasticity at synaptic boutons in
                      layer 4 of the adult rat 'barrel cortex'},
      journal      = {Brain structure $\&$ function},
      volume       = {220},
      number       = {6},
      issn         = {1863-2653},
      address      = {Berlin},
      publisher    = {Springer},
      reportid     = {FZJ-2014-05585},
      pages        = {3185-3209},
      year         = {2014},
      abstract     = {Excitatory layer 4 (L4) neurons in the ‘barrel field’
                      of the rat somatosensory cortex represent an important
                      component in thalamocortical information processing.
                      However, no detailed information exists concerning the
                      quantitative geometry of synaptic boutons terminating on
                      these neurons. Thus, L4 synaptic boutons were investigated
                      using serial ultrathin sections and subsequent quantitative
                      3D reconstructions. In particular, parameters representing
                      structural correlates of synaptic transmission and
                      plasticity such as the number, size and distribution of pre-
                      and postsynaptic densities forming the active zone (AZ) and
                      of the three functionally defined pools of synaptic vesicles
                      were analyzed. L4 synaptic boutons varied substantially in
                      shape and size; the majority had a single, but large AZ with
                      opposing pre- and postsynaptic densities that matched
                      perfectly in size and position. More than a third of the
                      examined boutons showed perforations of the postsynaptic
                      density. Synaptic boutons contained on average a total pool
                      of 561 ± 108 vesicles, with ~5 $\%$ constituting the
                      putative readily releasable, ~23 $\%$ the recycling, and the
                      remainder the reserve pool. These pools are comparably
                      larger than other characterized central synapses. Synaptic
                      complexes were surrounded by a dense network of fine
                      astrocytic processes that reached as far as the synaptic
                      cleft, thus regulating the temporal and spatial glutamate
                      concentration, and thereby shaping the unitary EPSP
                      amplitude. In summary, the geometry and size of AZs, the
                      comparably large readily releasable and recycling pools,
                      together with the tight astrocytic ensheathment, may explain
                      and contribute to the high release probability, efficacy and
                      modulation of synaptic transmission at excitatory L4
                      synaptic boutons. Moreover, the structural variability as
                      indicated by the geometry of L4 synaptic boutons, the
                      presence of mitochondria and the size and shape of the AZs
                      strongly suggest that synaptic reliability, strength and
                      plasticity is governed and modulated individually at
                      excitatory L4 synaptic boutons.},
      cin          = {INM-2},
      ddc          = {610},
      cid          = {I:(DE-Juel1)INM-2-20090406},
      pnm          = {331 - Signalling Pathways and Mechanisms in the Nervous
                      System (POF2-331)},
      pid          = {G:(DE-HGF)POF2-331},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000361566000008},
      doi          = {10.1007/s00429-014-0850-5},
      url          = {https://juser.fz-juelich.de/record/172036},
}