Analog Modulation of Mossy Fiber Transmission Is Uncoupled from Changes in Presynaptic Ca2+ Export

@article{citeulike:3064815, 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 {micro}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+. 10.1523/JNEUROSCI.1296-08.2008}, author = {Scott, Ricardo and Ruiz, Arnaud and Henneberger, Christian and Kullmann, Dimitri M. and Rusakov, Dmitri A.}, citeulike-article-id = {3064815}, citeulike-linkout-0 = {http://dx.doi.org/10.1523/JNEUROSCI.1296-08.2008}, citeulike-linkout-1 = {http://www.jneurosci.org/cgi/content/abstract/28/31/7765}, citeulike-linkout-2 = {http://view.ncbi.nlm.nih.gov/pubmed/18667608}, citeulike-linkout-3 = {http://www.hubmed.org/display.cgi?uids=18667608}, day = {30}, doi = {10.1523/JNEUROSCI.1296-08.2008}, journal = {J. Neurosci.}, keywords = {2pe, axon, ca3, ca\_phys, ephys, synapse}, month = {July}, number = {31}, pages = {7765--7773}, posted-at = {2008-08-04 15:19:20}, priority = {3}, title = {Analog Modulation of Mossy Fiber Transmission Is Uncoupled from Changes in Presynaptic Ca2+}, url = {http://dx.doi.org/10.1523/JNEUROSCI.1296-08.2008}, volume = {28}, year = {2008} }

TY - JOUR ID - citeulike:3064815 L3 - citeulike-article-id:3064815 N2 - 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 {micro}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+. 10.1523/JNEUROSCI.1296-08.2008 IS - 31 JF - J. Neurosci. EP - 7773 TI - Analog Modulation of Mossy Fiber Transmission Is Uncoupled from Changes in Presynaptic Ca2+ VL - 28 SP - 7765 KW - 2pe KW - axon KW - ca3 KW - ca_phys KW - ephys KW - synapse AU - Scott, Ricardo AU - Ruiz, Arnaud AU - Henneberger, Christian AU - Kullmann, Dimitri AU - Rusakov, Dmitri PY - 2008/07/30/ UR - http://dx.doi.org/10.1523/JNEUROSCI.1296-08.2008 ER -