Extracellular glutamate changes in rat striatum during ischemia determined by a novel dialysis electrode and conventional microdialysis.
Our newly developed method using a dialysis electrode has made it possible to perform real time monitoring of extracellular glutamate concentration ([Glu]e) utilizing the oxygen-independent reaction with glutamate oxidase and ferrocene. In this study, we therefore, investigated [Glu]e changes during brain ischemia using both the conventional microdialysis method and the dialysis electrode method. A comparison between our newly developed dialysis electrode and conventional microdialysis methods provided the following results. When the conventional microdialysis method was employed: (1) the elevation of [Glu]e during complete global ischemia was delayed; and (2) the elevation of concentration and reuptake of glutamate were delayed during 10-min transient ischemia, and the elevation of [Glu]e reached a maximum later using conventional microdialysis than using our dialysis electrode. (3) The biphasic [Glu]e elevation of glutamate concentration detected using the dialysis electrode method was not observed using the conventional microdialysis method. It was additionally investigated why the conventional microdialysis method provides inferior time resolution. In this study, we also demonstrated with the chromatographic SMART procedure coupled to UV detection that biogenic substances, i.e. low molecular weight proteins and peptides, are released during ischemic injury, and they may cause a delay in the time resolution in the microdialysis method.
Sugahara
M
M
Department of Pharmacology, Nihon University School of Medicine, Oyaguchi-Kami Machi, Itabashi-ku, 173, Tokyo, Japan.
Asai
S
S
Zhao
H
H
Nagata
T
T
Kunimatsu
T
T
Ishii
Y
Y
Kohno
T
T
Ishikawa
K
K
D000818:Animals; D002545:Brain Ischemia / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D003342:Corpus Striatum / Q000378:metabolism*; D004566:Electrodes; D005110:Extracellular Space / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism*; D008297:Male; D017551:Microdialysis; D051381:Rats; D017208:Rats, Wistar; D012680:Sensitivity and Specificity
D018698:Glutamic Acid