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Updated: May 2, 2026
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Fast Micro-iontophoresis of Glutamate and GABA: A Useful Tool to Investigate Synaptic Integration
Published on: July 31, 2013
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A local glutamate-glutamine cycle sustains synaptic excitatory transmitter release
Hiroaki Tani1, Chris G Dulla2, Zoya Farzampour3
1Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305, USA.
Neuron
|February 25, 2014
Summary
Astrocytes support excitatory neuron function by recycling glutamate. This study provides electrophysiological evidence that the astrocyte-glutamate-glutamine cycle is essential for maintaining active neurotransmission at nerve terminals.
Area of Science:
- Neuroscience
- Cellular Biology
- Neurochemistry
Background:
- Metabolic coupling between excitatory neurons and astrocytes is proposed to generate glutamate for release.
- The precise dependence of glutamatergic neurotransmission on this astrocytic support remains debated due to a lack of direct electrophysiological data.
Purpose of the Study:
- To provide direct electrophysiological evidence for the role of the astrocyte-glutamate-glutamine cycle in synaptic function.
- To investigate the localization and necessity of the glutamine-glutamate cycle at excitatory nerve terminals.
Main Methods:
- Utilized isolated nerve terminals in brain slices by transecting hippocampal Schaffer collaterals and cortical layer I axons.
- Applied alternating periods of high-frequency stimulation (20 Hz) and rest (0.2 Hz) to assess synaptic efficacy.
- Investigated the effects of inhibiting astrocytic glutamine synthetase and applying exogenous glutamine on glutamate release and synaptic function.
Main Results:
- Observed an activity-dependent reduction in synaptic efficacy correlating with decreased glutamate release during high-frequency stimulation.
- Demonstrated that inhibiting astrocytic glutamine synthetase enhanced this reduction, while exogenous glutamine reversed or prevented it.
- Confirmed these findings using in-vivo-derived natural stimuli at both network and cellular levels.
Conclusions:
- Provided direct electrophysiological evidence supporting the critical role of the astrocyte-dependent glutamate-glutamine cycle.
- Established that this metabolic coupling is required to sustain active neurotransmission at excitatory nerve terminals.
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