Brain extracellular space during spreading depression and ischemia.
The change of extracellular space volume of rat brain cortex during ischemia and cortical spreading depression, CSD (Leão 1944) was evaluated by a new method. The cortical surface was irrigated with isotonic CSF containing the extracellular markers 50 mM cholin or 50 mM trimethyltris(hydroxymethyl)methyl ammonium ion (N-TRIS), and their extracellular concentrations were monitored by ion-selective microelectrodes. When steady-state for the concentration of these markers was attained, CSD evoked a reversible increase of the concentration of the markers, indicating shrinkage of the interstitial volume of distribution. During ischemia an initial slow rate of concentration increase was observed, followed a few minutes later by a rapid increase concomitant with the sharp rise in extracellular potassium concentration. During CSD and ischemia, the maximal increases of choline and N-TRIS concentration reflected a shrinkage of the extracellular space amounting to about 50% of the initial volume.
D000818:Animals; D001921:Brain / Q000378:metabolism / Q000502:physiology*; D002794:Choline / Q000378:metabolism; D013181:Cortical Spreading Depression; D005110:Extracellular Space / Q000378:metabolism*; D002546:Ischemic Attack, Transient / Q000378:metabolism / Q000503:physiopathology*; D008297:Male; D008839:Microelectrodes; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D051381:Rats; D013997:Time Factors
D000644:Quaternary Ammonium Compounds; D002794:Choline