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Neuron. 2014 Apr 16;82(2):413-29. doi: 10.1016/j.neuron.2014.02.041.

Conditions and constraints for astrocyte calcium signaling in the hippocampal mossy fiber pathway.

Author information

1
Department of Physiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095-1751, USA.
2
Center for Neurobehavioral Genetics, Semel Institute for Neuroscience and Human Behavior, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095-1751, USA.
3
National Center for Microscopy and Imaging Research and Department of Neurosciences, University of California San Diego, La Jolla, CA 92093, USA.
4
Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA.
5
Department of Physiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095-1751, USA; Department of Neurobiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095-1751, USA. Electronic address: bkhakh@mednet.ucla.edu.

Abstract

The spatiotemporal activities of astrocyte Ca²⁺ signaling in mature neuronal circuits remain unclear. We used genetically encoded Ca²⁺ and glutamate indicators as well as pharmacogenetic and electrical control of neurotransmitter release to explore astrocyte activity in the hippocampal mossy fiber pathway. Our data revealed numerous localized, spontaneous Ca²⁺ signals in astrocyte branches and territories, but these were not driven by neuronal activity or glutamate. Moreover, evoked astrocyte Ca²⁺ signaling changed linearly with the number of mossy fiber action potentials. Under these settings, astrocyte responses were global, suppressed by neurotransmitter clearance, and mediated by glutamate and GABA. Thus, astrocyte engagement in the fully developed mossy fiber pathway was slow and territorial, contrary to that frequently proposed for astrocytes within microcircuits. We show that astrocyte Ca²⁺ signaling functionally segregates large volumes of neuropil and that these transients are not suited for responding to, or regulating, single synapses in the mossy fiber pathway.

PMID:
24742463
PMCID:
PMC4086217
DOI:
10.1016/j.neuron.2014.02.041
[Indexed for MEDLINE]
Free PMC Article

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