title: Most vesicles in a central nerve terminal participate in recycling.
abstract: Studies over the last decade using FM dyes to label vesicles at many terminals, including the calyx-type nerve terminal, led to a well accepted "principle" that only a small fraction of vesicles (∼5-20%) participate in recycling under physiological conditions. This principle imposes a large challenge in maintaining synaptic transmission during repetitive firing, because the small recycling pool may limit the number of available vesicles for release and nerve terminals would have to distinguish the recycling pool from the reserve pool and keep reserve pool vesicles from being used. By recording the presynaptic capacitance changes and the postsynaptic EPSC at rat calyx of Held synapses in the absence or presence of transmitter glutamate in nerve terminals, we developed a new method to count functional recycling vesicles. We found that essentially all vesicles in calyces participated in recycling, challenging the small-recycling-pool principle established by FM dye labeling. Nerve terminals may use all available vesicles to maximize their ability in maintaining synaptic transmission during repetitive firing.
authors.affiliation: Synaptic Transmission Section, National Institute of Neurological Disorders and Stroke, Bethesda, Maryland 20892, USA. lxue@fudan.edu.cn
authors.forename: Lei
authors.initials: L
authors.lastname: Xue
authors.forename: Jiansong
authors.initials: J
authors.lastname: Sheng
authors.forename: Xin-Sheng
authors.initials: XS
authors.lastname: Wu
authors.forename: Wei
authors.initials: W
authors.lastname: Wu
authors.forename: Fujun
authors.initials: F
authors.lastname: Luo
authors.forename: Wonchul
authors.initials: W
authors.lastname: Shin
authors.forename: Hsueh-Cheng
authors.initials: HC
authors.lastname: Chiang
authors.forename: Ling-Gang
authors.initials: LG
authors.lastname: Wu
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001703:Biophysics; D001933:Brain Stem / Q000166:cytology; D004558:Electric Stimulation; D004705:Endocytosis / Q000187:drug effects / Q000502:physiology*; D004791:Enzyme Inhibitors; D018683:Excitatory Amino Acid Agents / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology; D005260:Female; D018698:Glutamic Acid / Q000378:metabolism; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D066298:In Vitro Techniques; D007736:Kynurenic Acid / Q000494:pharmacology; D018942:Macrolides / Q000494:pharmacology; D008297:Male; D018408:Patch-Clamp Techniques; D017729:Presynaptic Terminals / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D009435:Synaptic Transmission / Q000502:physiology*; D013572:Synaptic Vesicles / Q000187:drug effects / Q000502:physiology*
chemical_list: D004791:Enzyme Inhibitors; D018683:Excitatory Amino Acid Agents; D018942:Macrolides; C104331:cyclopropyl-4-phosphonophenylglycine; D018698:Glutamic Acid; C040929:bafilomycin A1; D007736:Kynurenic Acid; D005998:Glycine