NS1643 increases fully activated Kv11.3 currents without shifting steady state inactivation curves.

<p>(A) The voltage dependence of steady-state inactivation of Kv11.3 channels was investigated by a triple pulse protocol consisting of two 500 ms depolarizations to +80 mV (P1 and P3), separated by a variable 250 ms test pulse to potentials between +80 and −120 mV (P2) to induce voltage dependent recovery from inactivation. (Aa) Current traces obtained before and after application of 10 µM NS1643. Control current transients obtained at the beginning of the P3 pulses are also shown on expanded time and voltage scale. (Ab) Means ± SEM (<i>n = 5</i>) of the charge flowing during the current transient elicited upon the P3 pulse are plotted against the preceding P2 test pulse potential. Data obtained before and after addition of NS1643 were normalized to the amplitude of the respective Boltzmann functions fitted to the charge values. (B, C) Data from similar experiments performed in external solution without Na⁺ (B, <i>n = 4</i>) or with low Ca²⁺ (C, <i>n = 4</i>). (Cb) Activation curves obtained from the same cells with an activation protocol as shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0050886#pone-0050886-g001" target="_blank">Fig. 1</a> are included in the diagram in gray.