Document Detail

Extracellular glutamate during focal cerebral ischaemia in rats: time course and calcium dependency.
MedLine Citation:
PMID:  7914220     Owner:  NLM     Status:  MEDLINE    
The time course of changes in extracellular glutamic acid levels and their Ca2+ dependency were studied in the rat striatum during focal cerebral ischaemia, using microdialysis. Ischaemia-induced changes were compared with those produced by high K(+)-evoked local depolarization. To optimize time resolution, glutamate was analysed continuously as the dialysate emerged from the microdialysis probe by either enzyme fluorimetry or biosensor. The Ca2+ dependency of glutamate changes was examined by perfusing the probe with Ca(2+)-free medium. With normal artificial CSF, ischaemia produced a biphasic increase in extracellular glutamate, which started from the onset of ischaemia. During the first phase lasting approximately 10 min, dialysate glutamate level increased from 5.8 +/- 0.9 microM.min-1 to 35.8 +/- 6.2 microM where it stabilized for approximately 3 min. During the second phase dialysate glutamate increased progressively to its maximum (82 +/- 8 microM), reached after 55 min of ischaemia, where it remained for as long as it was recorded (3 h). The overall changes in extracellular glutamate were similar when Ca2+ was omitted from the perfusion medium, except that the first phase was no longer detectable and, early in ischaemia, extracellular glutamate increased at a significantly slower rate than in the control group (2.2 +/- 1 microM.min-1; p < 0.05). On the basis of these data, we propose that most of the glutamate released in the extracellular space in severe ischaemia is of metabolic origin, probably originating from both neurons and glia, and caused by altered glutamate uptake mechanisms.(ABSTRACT TRUNCATED AT 250 WORDS)
F Wahl; T P Obrenovitch; A M Hardy; M Plotkine; R Boulu; L Symon
Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of neurochemistry     Volume:  63     ISSN:  0022-3042     ISO Abbreviation:  J. Neurochem.     Publication Date:  1994 Sep 
Date Detail:
Created Date:  1994-09-08     Completed Date:  1994-09-08     Revised Date:  2009-11-19    
Medline Journal Info:
Nlm Unique ID:  2985190R     Medline TA:  J Neurochem     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1003-11     Citation Subset:  IM    
Gough-Cooper Department of Neurological Surgery, Institute of Neurology, London, England.
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MeSH Terms
Action Potentials
Calcium / pharmacology*
Cerebral Arteries / physiology
Corpus Striatum / drug effects,  metabolism*
Cortical Spreading Depression
Extracellular Space / metabolism*
Glutamates / metabolism*
Glutamic Acid
Ischemic Attack, Transient / metabolism*
Potassium / pharmacology
Rats, Sprague-Dawley
Grant Support
//Wellcome Trust
Reg. No./Substance:
0/Glutamates; 56-86-0/Glutamic Acid; 7440-09-7/Potassium; 7440-70-2/Calcium

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