New Research In
Physical Sciences
Social Sciences
Featured Portals
Articles by Topic
Biological Sciences
Featured Portals
Articles by Topic
- Agricultural Sciences
- Anthropology
- Applied Biological Sciences
- Biochemistry
- Biophysics and Computational Biology
- Cell Biology
- Developmental Biology
- Ecology
- Environmental Sciences
- Evolution
- Genetics
- Immunology and Inflammation
- Medical Sciences
- Microbiology
- Neuroscience
- Pharmacology
- Physiology
- Plant Biology
- Population Biology
- Psychological and Cognitive Sciences
- Sustainability Science
- Systems Biology
Isolation of glutamate transport-coupled charge flux and estimation of glutamate uptake at the climbing fiber–Purkinje cell synapse
-
Edited by Roger A. Nicoll, University of California, San Francisco, CA (received for review December 8, 2003)

Abstract
Excitatory amino acid transporters (EAATs) located on neurons and glia are responsible for limiting extracellular glutamate concentrations, but specific contributions made by neuronal and glial EAATs have not been determined. At climbing fiber to Purkinje cell (PC) synapses in cerebellum, a fraction of released glutamate is rapidly bound and inactivated by neuronal EAATs located on postsynaptic PCs. Because transport involves a stoichiometric movement of ions and is electrogenic, postsynaptic currents mediated by EAATs should permit precise calculation of the amount of postsynaptic glutamate uptake. However, this is possible only if a stoichiometric EAAT current can be isolated from all other contaminating signals. We used synaptic stimulation and photolysis of caged glutamate to characterize the current in PCs that is resistant to high concentrations of glutamate receptor antagonists. Some of this response is inhibited by the high-affinity EAAT antagonist TBOA (dl-threo-β-benzyloxyaspartic acid), whereas the remaining current shows properties inconsistent with glutamate transport. By subtracting this residual non-EAAT current from the response recorded in glutamate receptor antagonists, we have obtained an estimate of postsynaptic uptake near physiological temperature. Analysis of such synaptic EAAT currents suggests that, on average, postsynaptic EAATs take up ≈1,300,000 glutamate molecules in response to a single climbing fiber action potential.
Footnotes
-
↵ * To whom correspondence should be addressed. E-mail: otist{at}ucla.edu.
-
This paper was submitted directly (Track II) to the PNAS office.
-
Abbreviations: EAAT, excitatory amino acid transporter; GluR, glutamate receptor; CF, climbing fiber; PC, Purkinje cell; NBQX, 2,3-dioxo-6-nitro-1,2,3,4-tetrahydrobenzo[f]quinoxaline-7-sulfonamide; GYKI 52466, 1-(4-aminophenyl)-4-methyl-7,8-methylenedioxy-5H-2,3-benzodiazepine hydrochloride; LY 367385, S-+-α-amino-4-carboxy-2-methylbenzeneacetic acid; CPP, RS-3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid; TBOA, dl-threo-β-benzyloxyaspartic acid; EPSC, excitatory postsynaptic current; AMPA, α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid; mGluR, metabotropic GluR; CPPG, RS-α-cyclopropyl-4-phosphophenylglycine.
- Copyright © 2004, The National Academy of Sciences