Effects of the anion channel blocker DIDS on ouabain-and high K+-induced release of amino acids from the rat cerebral cortex

Amino acid release from the rat cerebral cortex was analyzed using an in vi vo cortical cup perfusion model. Topical applications of ouabain or high ex tracellular K+ were used to mimic two dimensions of ischemic conditions whi ch promote cell swelling and amino acid release. Ouabain (30 mu M) induced significant releases of taurine, gamma-aminobutyric acid (GABA), aspartate, glutamate and phosphoethanolamine, The anion channel blocker, 4,4'-diisoth iocyanatostilbene-2, 2'-disulfonic acid (DIDS; 1 mM), inhibited ouabain-ind uced release of all these amino acids except for glutamate. Exposure to hig h extracellular K+ (75 mM) induced a delayed rise in the levels of taurine in the superfusates and an immediate increase in GABA levels. There were no significant releases of other amino acids. The release of taurine and GABA was sensitive to the blocking of anion channels with DIDS. Both ouabain- a nd high K+ induced taurine release is likely to be mediated by DIDS sensiti ve anion channels. The extracellular accumulation of the other amino acids, where insensitive to DIDS, may be mediated by mechanisms other than swelli ng-induced anion channels. (C) 2000 Elsevier Science Inc.