Effects of Glutamate Receptor Activation on Local Oxygen Changes

Apr 20, 2017 - plot representation of cyclic voltammetry data recorded around a 100 pulse, 20 Hz, 300 μA electrical stimulation as indicated by the g...
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The Effects of Glutamate Receptor Activation on Local Oxygen Changes Lindsay Walton, Nick G Boustead, Susan Carroll, and R. Mark Wightman ACS Chem. Neurosci., Just Accepted Manuscript • Publication Date (Web): 20 Apr 2017 Downloaded from http://pubs.acs.org on April 22, 2017

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ACS Chemical Neuroscience

The Effects of Glutamate Receptor Activation on Local Oxygen Changes

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Lindsay R Waltona

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Nick G Bousteada

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Susan Carrolla

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*R. Mark Wightmana,b

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a

Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA

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b

Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA

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Abstract

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Glutamate is ubiquitous throughout the brain and serves as the primary excitatory

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neurotransmitter. Neurons require energy to fire, and energetic substrates (i.e., O2, glucose) are

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renewed via cerebral blood flow (CBF) to maintain metabolic homeostasis. Magnetic resonance

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brain functionality studies rely on the assumption that CBF and neuronal activity are coupled

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consistently throughout the brain; however, the origin of neuronal activity does not always

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coincide with signals indicative of energy consumption (e.g., O2 decreases) at high spatial

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resolutions. Therefore, relationships between excitatory neurotransmission and energy use

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must be evaluated at higher resolutions. In this study, we showed that both endogenously

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released and exogenously ejected glutamate decrease local tissue O2 concentrations, but

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whether hyperemic O2 restoration followed depended on the stimulus method. Electrically

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stimulating the glutamatergic corticostriatal pathway evoked biphasic O2 responses at striatal

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terminals: first O2 decreased, then concentrations increased above baseline. Using

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iontophoresis to locally eject ionotropic glutamate receptor antagonists revealed that these

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receptors only influenced the O2 decrease. We compared electrical stimulation to iontophoretic

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glutamate stimulation, and measured concurrent single-unit activity and O2 to limit both

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stimulation and recordings to