Transient object recognition memory deficit and increase in intracellular Zn²⁺ after CA1 excitation.

<p>(A) The hippocampus was perfused with ACSF for 60 min to determine the basal concentration of extracellular zinc, and perfused with 100 mM KCl in ACSF for 40 min to determine the change in the extracellular zinc concentration by neuronal depolarization. The perfusate was collected every 20 min. The control represents the mean of 3 samples before perfusion with 100 mM KCl. The 100 mM KCl represents the mean of 2 samples during perfusion with 100 mM KCl. Each bar and line represents the mean ± SEM (n = 6). *, p<0.05, vs. control. (B) One week after implantation of guide cannulae as described in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0028615#s4" target="_blank">method</a> section, rats were placed for 10 min into an open field. Twenty-four hours after the open field exploration, vehicle (control, n = 9), 100 mM KCl in vehicle (n = 15), 100 mM KCl+1 mM CaEDTA in vehicle (n = 8), and 1 mM CaEDTA in vehicle (n = 7) were bilaterally injected via injection cannulae into the hippocampal CA1 of the rats at the rate of 0.5 µl/min for 2 min. Thirty minutes after injection, rats were trained for 5 min and then tested for 3 min in the novel object recognition task 1 h after training. In the case of 100 mM KCl injection into the CA1, 24 h after injection, rats were subjected to the test in the same manner. Each bar and line represents the mean ± SEM. ^#, p<0.05, ^##, p<0.01, vs. training; *, p<0.05, vs. control. (C) Hippocampal slices were prepared from rats, stained with ZnAF-2DA and immersed with ACSF (control,), 100 mM KCl and 100 mM KCl containing 1 mM CaEDTA for 15 min (n = 8). PLC, pyramidal cell layer. (D). Each bar and line (mean ± SEM) represents the rate (%) of the intensity of ZnAF-2 fluorescence in hippocampal slices immersed with 100 mM KCl or 100 mM KCl containing 1 mM CaEDTA to that immersed with ACSF, which was represented as 100%. **, p<0.01, vs. control; ^###, p<0.001, vs. KCl.