1. Conditions and Constraints for Astrocyte Calcium Signaling in the Hippocampal Mossy Fiber Pathway
- Author
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Jonathan S. Marvin, Sebastian Kracun, Ji Xu, Baljit S. Khakh, Xiaoping Tong, Mark H. Ellisman, Xiao-Hong Lu, Thomas J. O'Dell, X. William Yang, Eric A. Bushong, Olan Jackson-Weaver, Tiffany Shih, Loren L. Looger, and Martin D. Haustein
- Subjects
Male ,Action Potentials ,Inbred C57BL ,Receptors, Metabotropic Glutamate ,Hippocampus ,Transgenic ,Mice ,0302 clinical medicine ,Receptors ,Metabotropic Glutamate ,Hippocampal ,Psychology ,Premovement neuronal activity ,gamma-Aminobutyric Acid ,Hippocampal mossy fiber ,0303 health sciences ,General Neuroscience ,Glutamate receptor ,medicine.anatomical_structure ,Mossy Fibers, Hippocampal ,Excitatory postsynaptic potential ,Cognitive Sciences ,Female ,Sodium Channel Blockers ,Astrocyte ,medicine.drug ,Mossy fiber (hippocampus) ,GABA Agents ,Neuroscience(all) ,Glutamic Acid ,Mice, Transgenic ,In Vitro Techniques ,Biology ,Article ,gamma-Aminobutyric acid ,03 medical and health sciences ,medicine ,Neuropil ,Animals ,Calcium Signaling ,Excitatory Amino Acid Agents ,Mossy Fibers ,030304 developmental biology ,Neurology & Neurosurgery ,GABA-B ,Neurosciences ,Excitatory Postsynaptic Potentials ,Mice, Inbred C57BL ,Receptors, GABA-B ,Astrocytes ,Neuroscience ,030217 neurology & neurosurgery - Abstract
SummaryThe 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.
- Published
- 2014