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Analog modulation of mossy fiber transmission is uncoupled from changes in presynaptic Ca2+

Scott, R; Ruiz, A; Henneberger, C; Kullmann, DM; Rusakov, DA; (2008) Analog modulation of mossy fiber transmission is uncoupled from changes in presynaptic Ca2+. J NEUROSCI , 28 (31) 7765 - 7773. 10.1523/JNEUROSCI.1296-08.2008. Green open access

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Abstract

Subthreshold somatic depolarization has been shown recently to modulate presynaptic neurotransmitter release in cortical neurons. To understand the mechanisms underlying this mode of signaling in the axons of dentate granule cells (hippocampal mossy fibers), we have combined two- photon Ca2+ imaging with dual-patch recordings from somata and giant boutons forming synapses on CA3 pyramidal cells. In intact axons, subthreshold depolarization propagates both orthodromically and antidromically, with an estimated length constant of 200-600 mu m depending on the signal waveform. Surprisingly, presynaptic depolarization sufficient to enhance glutamate release at mossy fiber-CA3 pyramidal cell synapses has no detectable effect on either basal Ca2+-dependent fluorescence or action-potential-evoked fluorescence transients in giant boutons. We further estimate that neurotransmitter release varies with presynaptic Ca2+ entry with a 2.5-power relationship and that depolarization-induced synaptic facilitation remains intact in the presence of high-affinity presynaptic Ca2+ buffers or after blockade of local Ca2+ stores. We conclude that depolarization-dependent modulation of transmission at these boutons does not rely on changes in presynaptic Ca2+.

Type: Article
Title: Analog modulation of mossy fiber transmission is uncoupled from changes in presynaptic Ca2+
Open access status: An open access version is available from UCL Discovery
DOI: 10.1523/JNEUROSCI.1296-08.2008
Publisher version: http://dx.doi.org/10.1523/JNEUROSCI.1296-08.2008
Language: English
Additional information: This work is available to the public to copy, distribute, or display under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported license
Keywords: synaptic transmission, mossy fiber, analog modulation, hippocampus, dual-patch recordings, biophysical modeling, CALCIUM-CHANNELS, NEUROTRANSMITTER RELEASE, SYNAPTIC FACILITATION, BUFFER SATURATION, DYNAMICS, SYNAPSES, BOUTONS, CELLS, HIPPOCAMPUS, POTENTIALS
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > UCL Queen Square Institute of Neurology
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > UCL Queen Square Institute of Neurology > Clinical and Experimental Epilepsy
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > UCL School of Pharmacy
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > UCL School of Pharmacy > Pharmacology
URI: http://discovery.ucl.ac.uk/id/eprint/143066
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