6-cyano-7-nitroquinoxaline-2-3-dione and ethylisopropylamiloride

The effect of chemical anoxia (azide) in the presence of glucose on the free intracellular Ca2+ concentration ([Ca2+]i) and intracellular pH (pHi) in mouse neocortical neurons was investigated using Fura-2 and BCECF. Anoxia induced a reversible increase in [Ca2+]i which was significantly inhibited in nominally Ca2+-free medium. A change in pHo (8.2 or 6.6), or addition of NMDA and non-NMDA receptor antagonists (D-AP5 and CNQX) in combination, significantly reduced the increase in [Ca2+]i, pointing to a protective effect of extracellular alkalosis or acidosis, and involvement of excitatory amino acids. An initial anoxia-induced acidification was observed under all experimental conditions. In the control situation, this acidification was followed by a recovery/alkalinization of pHi in about 50% of the cells, a few cells showed no recovery, and some showed further acidification. EIPA, an inhibitor of Na+/H+ exchangers, prevented alkalinization, pointing towards anoxia-induced activation of a Na+/H+ exchanger. In a nominally Ca2+-free medium, the initial acidification was followed by a significant alkalinization. At pHo 8.2, the alkalinization was significantly increased, while at pHo 6.2, the initial acidification was followed by further acidification in about 50% of the cells, and by no further change in the remaining cells.

Topics: 2-Amino-5-phosphonovalerate; 6-Cyano-7-nitroquinoxaline-2,3-dione; Amiloride; Animals; Calcium; Cell Hypoxia; Cells, Cultured; Excitatory Amino Acid Antagonists; Extracellular Space; Female; Fluoresceins; Fura-2; Glucose; Hydrogen-Ion Concentration; Mice; Mice, Inbred Strains; Neocortex; Neurons; Sodium Azide; Sodium-Hydrogen Exchangers