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Changes in Extracellular Space Volume and
Geometry Induced by Cortical Spreading Depression in Immature
and Adult Rats
T. MAZEL1,2, F. RICHTER3,
L. VARGOVÁ1,2, E. SYKOVÁ1,2
1Department of Neuroscience, Institute of
Experimental Medicine, Academy of Sciences of the Czech Republic,
2Department of Neuroscience, Charles University,
Second Medical Faculty, Prague, Czech Republic and 3Department
of Physiology, Friedrich Schiller University, Jena, Germany
Summary
Changes in extracellular space (ECS) diffusion parameters, DC
potentials and extracellular potassium concentration were
studied during single and repeated cortical spreading
depressions (SD) in 13-15 (P13-15), 21 (P21) and 90-day-old
(adult) Wistar rats. The real-time iontophoretic method using
tetramethylammonium (TMA+)-selective microelectrodes was
employed to measure three ECS parameters in the somatosensory
cortex: the ECS volume fraction ( = ECS volume/total tissue
volume), ECS tortuosity (increase in diffusion path length)
and the nonspecific TMA+ uptake k’. SD was elicited by needle
prick. SD was significantly longer at P13-15 than at P21 and in
adults. During SD, in all age groups decreased from 0.21-0.23
to 0.05-0.09; increased from 1.55-1.65 to 1.95-2.07. Ten
minutes after SD, (in adults) and (all age groups) increased
compared to controls. This increase persisted even 1 hour after
SD. When SD was repeated at 1 hour intervals, both and
showed a gradual cumulative increase with SD repetition. Our
study also shows that cortical SD is, as early as P13,
accompanied by severe ECS shrinkage and increased diffusion path
length (tortuosity) with values similar to adults, followed by a
long-lasting increase in ECS volume and tortuosity when compared
to pre-SD values.
Key
words
Cell swelling • Cortex • Diffusion • Spreading depression •
Extracellular space
Reprint
requests
Prof. Eva Syková, M.D., D.Sc., Institute of Experimental
Medicine ASCR, Vídeňská 1083, 142 20 Prague, Czech Republic.
Phone: (+420) 2-4752204. FAX: (+420) 2-4752783. e-mail:
sykova@biomed.cas.cz
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