title: Systematic heterogeneity of fractional vesicle pool sizes and release rates of hippocampal synapses.
abstract: Hippocampal neurons in tissue culture develop functional synapses that exhibit considerable variation in synaptic vesicle content (20-350 vesicles). We examined absolute and fractional parameters of synaptic vesicle exocytosis of individual synapses. Their correlation to vesicle content was determined by activity-dependent discharge of FM-styryl dyes. At high frequency stimulation (30 Hz), synapses with large recycling pools released higher amounts of dye, but showed a lower fractional release compared to synapses that contained fewer vesicles. This effect gradually vanished at lower frequencies when stimulation was triggered at 20 Hz and 10 Hz, respectively. Live-cell antibody staining with anti-synaptotagmin-1-cypHer 5, and overexpression of synaptopHluorin as well as photoconversion of FM 1-43 followed by electron microscopy, consolidated the findings obtained with FM-styryl dyes. We found that the readily releasable pool grew with a power function with a coefficient of 2/3, possibly indicating a synaptic volume/surface dependency. This observation could be explained by assigning the rate-limiting factor for vesicle exocytosis at high frequency stimulation to the available active zone surface that is proportionally smaller in synapses with larger volumes.
authors.affiliation: Department of Psychiatry and Psychotherapy, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Welzel
authors.affiliation: Department of Physiology, Faculty of Medicine, Jabriya, Kuwait University, Safat, Kuwait.
authors.forename: Andreas W
authors.initials: AW
authors.lastname: Henkel
authors.affiliation: Department of Psychiatry and Psychotherapy, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Armin M
authors.initials: AM
authors.lastname: Stroebel
authors.affiliation: Department of Psychiatry and Psychotherapy, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Jasmin
authors.initials: J
authors.lastname: Jung
authors.affiliation: Department of Psychiatry and Psychotherapy, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Carsten H
authors.initials: CH
authors.lastname: Tischbirek
authors.affiliation: Department of Psychiatry and Psychotherapy, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Katrin
authors.initials: K
authors.lastname: Ebert
authors.affiliation: Department of Psychiatry and Psychotherapy, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Kornhuber
authors.affiliation: European Neuroscience Institute Göttingen, Deutsche Forschungsgemeinschaft Research Center for Molecular Physiology of the Brain/Excellence Cluster 171, Göttingen, Germany.
authors.forename: Silvio O
authors.initials: SO
authors.lastname: Rizzoli
authors.affiliation: Department of Psychiatry and Psychotherapy, University of Erlangen-Nuremberg, Erlangen, Germany. Electronic address: teja.groemer@uk-erlangen.de.
authors.forename: Teja W
authors.initials: TW
authors.lastname: Groemer
mesh_terms: D000818:Animals; D016477:Artifacts; D004705:Endocytosis; D005089:Exocytosis; D005456:Fluorescent Dyes / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D007700:Kinetics; D008856:Microscopy, Fluorescence; D011726:Pyridinium Compounds / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013499:Surface Properties; D013572:Synaptic Vesicles / Q000378:metabolism* / Q000648:ultrastructure; D013997:Time Factors
chemical_list: C073804:FM1 43; D005456:Fluorescent Dyes; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds