Extracellular ion concentrations during spreading depression and ischemia in the rat brain cortex.
We compared interstitial ion concentrations in rat brain cortex during two conditions where pronounced changes are observed: spreading depression and ischemia. Initially, during the two phenomena, an increase of [K+]e from 3 to approximately 10 mM were observed, but only small changes of the other ion concentrations. Hereafter, [K+]e exhibited a rapid increase (2-3 s) to 55 mM, whereas [Na+]e rapidly decreased to 60 mM, [Cl-]e to 75 mM, and [Ca++]e to 0.08 mM. The changes were accompanied by a rapid negative shift in the local electrical potential. However, there were differences in the ionic events during the two phenomena. In spreading depression, the initial [K+]e increase took place in 5-10 s, but in ischemia it lasted 1-2 min. The ionic perturbations were spontaneously reverted in SD, but in ischemia they proceeded further and reached after 5 min (mM): [K+]e 75, [Na+]e 50, [Cl-]e 72, and [Ca++]e 0.06. The similar chain of ionic events during spreading depression and ischemia suggests a common mechanism for the ionic changes, probably involving changes of ionic permeability of brain cells.
D000818:Animals; D002545:Brain Ischemia / Q000378:metabolism*; D002118:Calcium / Q000032:analysis; D002540:Cerebral Cortex / Q000032:analysis; D002712:Chlorides / Q000032:analysis; D013181:Cortical Spreading Depression; D005110:Extracellular Space / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D008297:Male; D011188:Potassium / Q000032:analysis; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000032:analysis
D002712:Chlorides; D012964:Sodium; D011188:Potassium; D002118:Calcium