caa a22 4500 606201718 CHVBK 20210128100949.0 cr unu---uuuuu 210128e20151101xx s 000 0 eng 10.1007/s00429-014-0850-5 doi (NATIONALLICENCE)springer-10.1007/s00429-014-0850-5 Structural determinants underlying the high efficacy of synaptic transmission and plasticity at synaptic boutons in layer 4 of the adult rat ‘barrel cortex' [Elektronische Daten] [Astrid Rollenhagen, Kerstin Klook, Kurt Sätzler, Guanxiao Qi, Max Anstötz, Dirk Feldmeyer, Joachim Lübke] 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. Springer-Verlag Berlin Heidelberg, 2014 Barrel cortex nationallicence Layer 4 synaptic boutons nationallicence Quantitative 3D reconstructions nationallicence Distinct pools of synaptic vesicles nationallicence Synaptic transmission and plasticity nationallicence Rollenhagen Astrid Institute of Neuroscience and Medicine INM-2, Research Centre Jülich GmbH, Leo-Brandt Str., 52425, Jülich, Germany aut Klook Kerstin Institute of Neuroscience and Medicine INM-2, Research Centre Jülich GmbH, Leo-Brandt Str., 52425, Jülich, Germany aut Sätzler Kurt School of Biomedical Sciences, University of Ulster, Cromore Rd., BT52 1SA, Londonderry, UK aut Qi Guanxiao Institute of Neuroscience and Medicine INM-2, Research Centre Jülich GmbH, Leo-Brandt Str., 52425, Jülich, Germany aut Anstötz Max Institute of Neuroscience and Medicine INM-2, Research Centre Jülich GmbH, Leo-Brandt Str., 52425, Jülich, Germany aut Feldmeyer Dirk Institute of Neuroscience and Medicine INM-2, Research Centre Jülich GmbH, Leo-Brandt Str., 52425, Jülich, Germany aut Lübke Joachim Institute of Neuroscience and Medicine INM-2, Research Centre Jülich GmbH, Leo-Brandt Str., 52425, Jülich, Germany aut Brain Structure and Function Springer Berlin Heidelberg 220/6(2015-11-01), 3185-3209 1863-2653 220:6<3185 2015 220 429 https://doi.org/10.1007/s00429-014-0850-5 text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s00429-014-0850-5 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Rollenhagen Astrid Institute of Neuroscience and Medicine INM-2, Research Centre Jülich GmbH, Leo-Brandt Str., 52425, Jülich, Germany aut NATIONALLICENCE 700 1- Klook Kerstin Institute of Neuroscience and Medicine INM-2, Research Centre Jülich GmbH, Leo-Brandt Str., 52425, Jülich, Germany aut NATIONALLICENCE 700 1- Sätzler Kurt School of Biomedical Sciences, University of Ulster, Cromore Rd., BT52 1SA, Londonderry, UK aut NATIONALLICENCE 700 1- Qi Guanxiao Institute of Neuroscience and Medicine INM-2, Research Centre Jülich GmbH, Leo-Brandt Str., 52425, Jülich, Germany aut NATIONALLICENCE 700 1- Anstötz Max Institute of Neuroscience and Medicine INM-2, Research Centre Jülich GmbH, Leo-Brandt Str., 52425, Jülich, Germany aut NATIONALLICENCE 700 1- Feldmeyer Dirk Institute of Neuroscience and Medicine INM-2, Research Centre Jülich GmbH, Leo-Brandt Str., 52425, Jülich, Germany aut NATIONALLICENCE 700 1- Lübke Joachim Institute of Neuroscience and Medicine INM-2, Research Centre Jülich GmbH, Leo-Brandt Str., 52425, Jülich, Germany aut NATIONALLICENCE 773 0- Brain Structure and Function Springer Berlin Heidelberg 220/6(2015-11-01), 3185-3209 1863-2653 220:6<3185 2015 220 429