title: Presynaptic Ca2+ requirements and developmental regulation of posttetanic potentiation at the calyx of Held.
abstract: Large excitatory synapses in the auditory system, such as the calyx of Held, faithfully transmit trains of action potentials up to a frequency of a few hundred hertz, and these synapses are thought to display a limited repertoire of synaptic plasticity. Here, we show that brief trains of 100 Hz stimulation induce posttetanic potentiation (PTP) of transmitter release at the calyx of Held. In young rats [postnatal day 4 (P4) to P6], PTP could be induced with shorter 100 Hz trains compared with older age groups (P8-P10 and P12-P14), but the maximal amount of PTP was similar, with 200% of control EPSC amplitude. The size of the readily releasable pool of vesicles was not increased significantly during PTP. Bath application of the membrane-permeable Ca2+ chelator EGTA-AM suppressed PTP, indicating a role for presynaptic Ca2+ in PTP at the calyx of Held. Presynaptic Ca2+ imaging showed that the intracellular Ca2+ concentration, [Ca2+]i, was increased by 40-120 nM at the peak of PTP, and this "residual" [Ca2+]i decayed in parallel with PTP, with time constants in the range of 10-60 s. During whole-cell recording of the presynaptic calyx of Held, PTP was absent, and the decay of residual [Ca2+]i was strongly accelerated. The data show that the calyx of Held expresses a mechanism of transmitter release potentiation in which a small, sustained elevation of basal [Ca2+]i increases the transmitter release probability after trains of high-frequency stimulation.
authors.affiliation: AG Synaptische Dynamik und Modulation and Abteilung Membranbiophysik, Max-Planck-Institut für Biophysikalische Chemie, D-37077 Göttingen, Germany.
authors.forename: Natalya
authors.initials: N
authors.lastname: Korogod
authors.forename: Xuelin
authors.initials: X
authors.lastname: Lou
authors.forename: Ralf
authors.initials: R
authors.lastname: Schneggenburger
mesh_terms: D000367:Age Factors; D000814:Aniline Compounds; D000818:Animals; D000831:Animals, Newborn; D001581:Benzothiadiazines / Q000494:pharmacology; D001933:Brain Stem / Q000166:cytology; D002118:Calcium / Q000378:metabolism*; D003952:Diagnostic Imaging / Q000379:methods; D004307:Dose-Response Relationship, Radiation; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004558:Electric Stimulation; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D018698:Glutamic Acid / Q000378:metabolism; D066298:In Vitro Techniques; D007736:Kynurenic Acid / Q000494:pharmacology; D009473:Neuronal Plasticity / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects*; D009474:Neurons / Q000166:cytology; D010080:Oxazoles; D018408:Patch-Clamp Techniques / Q000379:methods; D017729:Presynaptic Terminals / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D013569:Synapses / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D013997:Time Factors
chemical_list: D000814:Aniline Compounds; D001581:Benzothiadiazines; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; C500962:Fura-4F; D010080:Oxazoles; D018698:Glutamic Acid; D004533:Egtazic Acid; C046770:EGTA acetoxymethyl ester; D007736:Kynurenic Acid; C004639:cyclothiazide; D002118:Calcium