Calcium-triggered fusion of synaptic vesicles and neurotransmitter release are fundamental signalling steps in the central nervous system. It is generally assumed that fast transmitter release is triggered by elevations in intracellular calcium concentration ([Ca2+]i) to at least 100 µM near the sites of vesicle fusion1,2,3,4,5. For synapses in the central nervous system, however, there are no experimental estimates of this local [Ca2+]i signal. Here we show, by using calcium ion uncaging in the large synaptic terminals of the calyx of Held, that step-like elevations to only 10 µM [Ca2+] i induce fast transmitter release, which depletes around 80% of a pool of available vesicles in less than 3 ms. Kinetic analysis of transmitter release rates after [Ca2+]i steps revealed the rate constants for calcium binding and vesicle fusion. These show that transient (around 0.5 ms) local elevations of [Ca2+]i to peak values as low as 25 µM can account for transmitter release during single presynaptic action potentials. The calcium sensors for vesicle fusion are far from saturation at normal release probability. This non-saturation, and the high intracellular calcium cooperativity in triggering vesicle fusion, make fast synaptic transmission very sensitive to modulation by changes in local [Ca2+]i.
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Adler, E. M., Augustine, G. J., Duffy, S. N. & Charlton, M. P. Alien intracellular calcium chelators attenuate neurotransmitter release at the squid giant synapse. J. Neurosci. 11, 1496–1507 (1991).
Llinás, R., Sugimori, M. & Silver, R. B. Microdomains of high calcium concentration in a presynaptic terminal. Science 256, 677– 679 (1992).
Yamada, W. M. & Zucker, R. S. Time course of transmitter release calculated from simulations of a calcium diffusion model. Biophys. J. 61, 671–682 ( 1992).
Heidelberger, R., Heinemann, C., Neher, E. & Matthews, G. Calcium dependence of the rate of exocytosis in a synaptic terminal. Nature 371, 513–515 (1994).
Roberts, W. M. Localization of calcium signals by a mobile calcium buffer in frog saccular hair cells. J. Neurosci. 14, 3246– 3262 (1994).
Forsythe, I. D. Direct patch recording from identified presynaptic terminals mediating glutamatergic EPSCs in the rat CNS, in vitro. J. Physiol. 479, 381–387 (1994).
Borst, J. G. G., Helmchen, F. & Sakmann, B. Pre- and postsynaptic whole-cell recordings in the medial nucleus of the trapezoid body of the rat. J. Physiol. 489, 825–840 (1995).
Naraghi, M., Müller, T. H. & Neher, E. Two-dimensional determination of the cellular Ca2+ binding in bovine chromaffin cells. Biophys. J. 75, 1635–1647 (1998).
Thomas, P., Wong, J. G. & Almers, W. Millisecond studies of secretion in single rat pituitary cells stimulated by flash photolysis of caged Ca2+. EMBO J. 12, 303–306 ( 1993).
Heinemann, C., Chow, R. H., Neher, E. & Zucker, R. S. Kinetics of the secretory response in bovine chromaffin cells following flash photolysis of caged Ca2+. Biophys. J. 67, 2546–2557 (1994).
Yamada, K. A. & Tang, C.-M. Benzothiazides inhibit rapid glutamate receptor desensitization and enhance glutamatergic synaptic currents. J. Neurosci. 13, 3904–3915 (1993).
Trussell, L. O., Zhang, S. & Raman, I. M. Desensitization of AMPA receptors upon multiquantal neurotransmitter release. Neuron 10, 1185 –1196 (1993).
Borst, J. G. G. & Sakmann, B. Calcium influx and transmitter release in a fast CNS synapse. Nature 383, 431–434 (1996).
Schneggenburger, R., Meyer, A. C. & Neher, E. Released fraction and total size of a pool of immediately available transmitter quanta at a calyx synapse. Neuron 23, 399–409 (1999).
van der Kloot, W. Estimating the timing of quantal releases during end-plate currents at the frog neuromuscular junction. J. Physiol. 402, 595–603 (1988).
Diamond, J. S. & Jahr, C. E. Asynchronous release of synaptic vesicles determines the time course of the AMPA receptor-mediated EPSC. Neuron 15, 1097–1107 (1995).
Wu, L. -G. & Borst, J. G. G. The reduced release probability of releasable vesicles during recovery from short-term synaptic depression. Neuron 23, 821–832 (1999).
Dodge, F. A. & Rahamimoff, R. Co-operative action of calcium ions in transmitter release at the neuromuscular junction. J. Physiol. 193, 419–432 ( 1967).
Landò, L. & Zucker, R. S. Ca2+ cooperativity in neurosecretion measured using photolabile Ca2+ chelators. J. Neurophysiol. 72, 825–830 (1994).
Barnes-Davies, M. & Forsythe, I. D. Pre- and postsynaptic glutamate receptors at a giant excitatory synapse in rat auditory brainstem slices. J. Physiol. 488, 387– 406 (1995).
Lagnado, L., Gomis, A. & Job, C. Continuous vesicle cycling in the synaptic terminal of retinal bipolar cells. Neuron 17, 957–967 (1996).
Ohana, O. & Sakmann, B. Transmitter release modulation in nerve terminals of rat neocortical pyramidal cells by intracellular calcium buffers. J. Physiol. 513, 135– 148 (1998).
Helmchen, F., Borst, J. G. G. & Sakmann, B. Calcium dynamics associated with a single action potential in a CNS presynaptic terminal. Biophys. J. 72, 1458–1471 (1997).
Goda, Y. & Südhof, T. Calcium regulation of neurotransmitter release: reliably unreliable? Curr. Opin. Cell Biol. 9, 513–518 (1997).
Wu, L. -G. & Saggau, P. Presynaptic inhibition of elicited neurotransmitter release. Trends Neurosci. 20, 204–212 (1997).
Zucker, R. S. Calcium- and activity-dependent synaptic plasticity. Curr. Opin. Neurobiol. 9, 305–313 ( 1999).
Zucker, R. S. Effects of photolabile calcium chelators on fluorescent calcium indicators. Cell Calcium 13, 29–40 (1992).
Traynelis, S. F. Software-based correction of single compartment series resistance errors. J. Neurosci. Methods 86, 25– 34 (1998).
Xu, T., Naraghi, M., Kang, H. & Neher, E. Kinetic studies of Ca2+ binding and Ca2+ clearance in the cytosol of adrenal chromaffin cells. Biophys. J. 73, 532–545 (1997).
Xu-Friedman, M. A. & Regehr, W. G. Presynaptic strontium dynamics and synaptic transmission. Biophys. J. 76, 2029–2042 (1999).
Bollmann, J. H., Sakmann, B. & Borst, J. G. G. Calcium sensitivity of glutamate release in a calyx-type terminal. Science (in the press).
We thank T. Sakaba for discussions, and J. Rettig, M. Casado, P. Ascher and R. Fernández-Chacon for critical comments on the manuscript. This work was supported by the Deutsche Forschungsgemeinschaft.
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Schneggenburger, R., Neher, E. Intracellular calcium dependence of transmitter release rates at a fast central synapse. Nature 406, 889–893 (2000). https://doi.org/10.1038/35022702
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