Depolarization-induced 65zinc influx into cultured cortical neurons

Toxic Zn2+ influx may be a key mechanism underlying selective neuronal death after transient global ischemia in rats. To identify routes responsible for neuronal Zn2+ influx, we measured the accumulation of (65)Zin(2+) into cultured murine cortical cells under depolarizing conditions (60 mM K+) associated with severe hypoxia-ischemia in brain tissue. Addition of 60 mM K+ or 300 muM kainate substantially increased Zn-65(2+) accumulation into mixed cultures of neurons and glia, but not glia alone. Zn-65(2+) accumulation was attenuated by increasing concentrations of extracellular Ca2+ or trypsin pretreatment , but not by late trypsinization, and corresponded to an increase in atomic Zn2+. Confirming predominantly neuronal entry, K+-induced Zn-65(2+) accumulation was reduced by prior selective destruction of neurons with NMDA. K+-induced Zn-65(2+) influx was not sensitive to glutamate receptor antagonists, but was attenuated by Gd3+ and Cd2+ as well as 1 muM nimodipine; it was partially sensitive to 1 muM omega-conotoxin-GVIA, and insensitive to 1 muM omega-agatoxin-IVA. K+-induced, Gd3+-sensitive Ca-45(2+) accumulation but not Zn-65(2+) accumulation was sharply attenuated by lowering extracellular pH to 6.6. (C) 2002 Elsevier Science (USA).