Figure 2.

Expression of Kv4.2DN reduces peak outward K⁺ currents and eliminates the rapid component of current decay (I_A) in cortical pyramidal neurons. A, Whole-cell Kv currents were recorded (as described in the legend to Fig. 1) from cortical pyramidal neurons expressing EGFP alone or EGFP and Kv4.2DN. As is evident, the waveforms of the currents recorded from cells expressing Kv4.2DN plus EGFP (right panel) are distinct from those recorded from cells expressing EGFP alone (left panel). B, Mean ± SEM (n = 25) peak outward K⁺ current densities are reduced significantly (p < 0.001) at all test potentials in Kv4.2DN plus EGFP-expressing cells. C, In contrast, mean ± SEM plateau outward K⁺ current densities in cells expressing Kv4.2DN plus EGFP and cells expressing EGFP alone are not significantly different. D, E, Exponential fits (plotted as lines in red) to the decay phases of the outward K⁺ currents (plotted as points in black) in EGFP-expressing (D) and Kv4.2DN plus EGFP-expressing (E) cells are displayed. D, E, Insets, The currents (plotted as points in black) at the more positive potentials are displayed on an expanded time scale with the fits (plotted as lines in red) superimposed. The decay phases of the outward currents in cells expressing EGFP alone (D) are not well described by the sum of two exponentials (Da), and three components (Db) are required to fit the experimental data; the arrows are placed to illustrate the differences in the quality of the fits with two (Da) and three (Db) exponential components. In cells expressing Kv4.2DN and EGFP (E), in contrast, the rapid component of current decay is not evident, and the decay phases of the currents are well described (Ea) by the sum of two exponentials. Error bars represent SEM.