Abstract
Astrocytes are electrically nonexcitable cells that display increases in cytosolic calcium ion (Ca²+) in response to various neurotransmitters and neuromodulators. However, the physiological role of astrocytic Ca²+ signaling remains controversial. We show here that astrocytic Ca²+ signaling ex vivo and in vivo stimulated the Na+,K+-ATPase (Na+- and K+-dependent adenosine triphosphatase), leading to a transient decrease in the extracellular potassium ion (K+) concentration. This in turn led to neuronal hyperpolarization and suppressed baseline excitatory synaptic activity, detected as a reduced frequency of excitatory postsynaptic currents. Synaptic failures decreased in parallel, leading to an increase in synaptic fidelity. The net result was that astrocytes, through active uptake of K+, improved the signal-to-noise ratio of synaptic transmission. Active control of the extracellular K+ concentration thus provides astrocytes with a simple yet powerful mechanism to rapidly modulate network activity.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Adenosine Triphosphate / pharmacology
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Animals
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Animals, Newborn
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Astrocytes / cytology
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Astrocytes / metabolism
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Astrocytes / physiology*
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Biological Transport / drug effects
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Calcium / metabolism*
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Calcium Signaling / physiology
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Cells, Cultured
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Excitatory Postsynaptic Potentials / physiology
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Extracellular Space / metabolism
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Hippocampus / cytology
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Hippocampus / metabolism
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Mice
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Mice, Inbred C57BL
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Microscopy, Confocal
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Nerve Net / metabolism
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Nerve Net / physiology
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Neurons / cytology
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Neurons / metabolism
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Neurons / physiology
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Ouabain / pharmacology
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Potassium / metabolism*
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Rats
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Rats, Wistar
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Receptors, G-Protein-Coupled / agonists
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Receptors, G-Protein-Coupled / physiology
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Rubidium Radioisotopes / metabolism
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Sodium-Potassium-Exchanging ATPase / metabolism
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Synaptic Transmission / physiology*
Substances
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Receptors, G-Protein-Coupled
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Rubidium Radioisotopes
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Ouabain
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Adenosine Triphosphate
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Sodium-Potassium-Exchanging ATPase
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Potassium
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Calcium