Intracellular calcium in NCB-20 cells: elevation by depolarization and ethanol but not by glutamate.

Intracellular Ca2+, measured in NCB-20 cells with the fluorescent indicator fura-2, was elevated by K(+)-depolarization and by ethanol, but not by the excitatory amino acids L-glutamate and N-methyl-D-aspartate. These amino acids failed to raise intracellular Ca2+ levels even in the presence of elevated extracellular Ca2+, in the absence of extracellular Mg2+ or Na+, under depolarizing conditions, or in differentiated cells, and induced neither 45Ca2+ uptake nor excitotoxic cell death. NCB-20 cells thus appear to express functional voltage-gated, but not N-methyl-D-aspartate receptor-gated, Ca2+ channels.