Glutamate triggers preferential Zn2+ flux through Ca2+ permeable AMPA channels and consequent ROS production

ZN2+ co-released with glutamate at excitatory synaptic sites can enter and cause injury to postsynaptic neurons. While prior studies using the slowly desensitizing agonist kainate suggested preferential Zn2+ permeation through Ca2+ permeable AMPA/kainate (Ca-A/K) channels, the present study aims to assess relevance of those findings upon more physiological receptor activation. Microfluorimetric techniques were used to measure [Zn2+]i attained upon exposure to the rapidly desensitizing agonist AMPA or to the physiological agonist glutamate, in the presence of 300 microM Zn2+. Under these conditions, micromolar [Zn2+]i rises (delta[Zn2+]i) were still observed to occur selectively in the subset of neurons that express large numbers of Ca-A/ K channels. Further studies using the oxidation sensitive dye, hydroethidine, revealed Zn2+-dependent reactive oxygen species generation that paralleled delta[Zn2+]i, with rapid oxidation only observed in the case of Zn2+ entry through Ca-A/K channels.