An ATP-driven Cl- pump regulates Cl- concentrations in rat hippocampal neurons.

To investigate the role of Cl(-)-stimulated Mg(2+)-ATPase (Cl(-)-ATPase) in neurons, we examined the effects of ethacrynic acid (0.3 mM), which completely inhibits Cl(-)-ATPase on the intracellular Cl- concentrations of cultured rat hippocampal neurons, using Cl(-)-sensitive fluorescent probes. Ethacrynic acid and ATP consuming treatment increased the intracellular Cl- concentration, but elevation of the extracellular K+ concentration up to 10 mM, inhibition of Na+/K(+)-ATPase, or dissolution of H+ gradients had no effect. Furosemide (0.1 mM), an inhibitor of Na+/K+/Cl- co-transport, decreased the intracellular Cl- concentrations. These results indicate that an ethacrynic acid-sensitive and ATP-driven Cl- pump functions to reduce intraneural Cl- concentrations.