FIGURE 4.

Effect of metastable Zn²⁺-Aβ40 oligomers on primary hippocampal neurons. a, top panels, gradual rise in basal [Ca²⁺]_i in cultured neurons. Bottom panels, Ca²⁺-influx peaks. b, Ca²⁺-imaging of the same fields after background subtraction. The y axis represents Fluo-4AM fluorescence under carefully standardized experimental conditions, including dye-loading time, temperature, light-source intensity, detector offset, and gain. c, net change of spontaneous [Ca²⁺]_i bursts in the presence of Aβ40 monomers (green), Aβ40 fibrils (blue), Zn²⁺ (purple), or metastable Zn²⁺-Aβ40 oligomers (red). Negative values are relative to the initial [Ca²⁺]_i burst rate. d, resting [Ca²⁺]_i in the same population of neurons. The y axis represents Fluo-4AM fluorescence under the same standardized conditions as in b and corresponds to the values of the net [Ca²⁺]_i changes obtained after subtracting initial [Ca²⁺]_i. e, viability of neurons at t = 72 h measured by immunostaining for neuron-specific enolase. The data are presented as mean ± S.E. for three independent experiments compared with the control. N.S., non-significant.