A study finds that human activity has led to a severe decrease in Caribbean shark abundance.
Image credit: Sean Mattson (International Center for Tropical Agriculture, Cali, Colombia).
-
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
Isolation of glutamate transport-coupled charge flux and estimation of glutamate uptake at the climbing fiber–Purkinje cell synapse
Sign up for Article Alerts
Jump to section
You May Also be Interested in
A study suggests that male dragonflies will evolve smaller melanin wing patches by 2070 as global warming continues.
Image credit: Pixabay/liggraphy.
The largest pandemic-related declines in nitrogen dioxide pollution occurred in the least White census tracts in the United States, which nonetheless faced higher levels during the pandemic than most White communities before the pandemic.
Image credit: Pixabay/SD-Pictures.
A special kind of electrical discharge generated near the base of the plume could provide researchers with a heads-up that an eruption has started.
Image credit: NASA/Mike Barratt (photographer).
Genome editing technology has grown too quickly, and stakeholders in the debate are too diverse, for current approaches to establish a robust regulatory regime.
Image credit: Shutterstock/vchal.