Abstract
Although astrocytes are the most abundant cell type in the brain, evidence for their activation during physiological sensory activity is lacking. Here we show that whisker stimulation evokes increases in astrocytic cytosolic calcium (Ca(2+)) within the barrel cortex of adult mice. Increases in astrocytic Ca(2+) were a function of the frequency of stimulation, occurred within several seconds and were inhibited by metabotropic glutamate receptor antagonists. To distinguish between synaptic input and output, local synaptic activity in cortical layer 2 was silenced by iontophoresis of AMPA and NMDA receptor antagonists. The antagonists did not reduce astrocytic Ca(2+) responses despite a marked reduction in excitatory postsynaptic currents in response to whisker stimulation. These findings indicate that astrocytes respond to synaptic input, by means of spillover or ectopic release of glutamate, and that increases in astrocytic Ca(2+) occur independently of postsynaptic excitatory 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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Afferent Pathways / physiology*
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Animals
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Astrocytes / drug effects
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Astrocytes / metabolism*
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Calcium / metabolism
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Calcium Signaling / drug effects
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Calcium Signaling / physiology*
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Cell Communication / drug effects
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Cell Communication / physiology
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Excitatory Amino Acid Antagonists / pharmacology
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Excitatory Postsynaptic Potentials / drug effects
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Excitatory Postsynaptic Potentials / physiology
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Female
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Male
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Mechanoreceptors / physiology*
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Mice
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Physical Stimulation
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Reaction Time / drug effects
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Reaction Time / physiology
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Receptors, AMPA / antagonists & inhibitors
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Receptors, AMPA / metabolism
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Receptors, Metabotropic Glutamate / agonists
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Receptors, Metabotropic Glutamate / metabolism
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Receptors, N-Methyl-D-Aspartate / antagonists & inhibitors
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Receptors, N-Methyl-D-Aspartate / metabolism
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Somatosensory Cortex / cytology
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Somatosensory Cortex / physiology*
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Synaptic Transmission / drug effects
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Synaptic Transmission / physiology
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Touch / physiology*
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Up-Regulation / drug effects
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Up-Regulation / physiology
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Vibrissae / innervation
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Vibrissae / physiology
Substances
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Excitatory Amino Acid Antagonists
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Receptors, AMPA
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Receptors, Metabotropic Glutamate
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Receptors, N-Methyl-D-Aspartate
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Calcium