Table 1.

Effect of 10 µM NS5806 on K_v4 channels in absence or presence of KChIP2

	Kv4.1	Kv4.1/KChIP2	Kv4.2	Kv4.2/KChIP2	Kv4.3	Kv4.3/KChIP2
Peak current (µA) control	12.2 ± 1.1	23.6 ± 1.3	1.9 ± 0.3	6.6 ± 1.4	13.8 ± 1.2	23.2 ± 1.2
10 µM NS5806	12.6 ± 1.0 (5)	27.0 ± 1.3 (6)***	2.0 ± 0.3 (6)	7.5 ± 1.3 (10)*	15.3 ± 1.4 (11)	26.9 ± 1.3 (9)***
Decay τ (ms) control	45.4 ± 1.2	63.6 ± 5.5	24.2 ± 1.1 (6)	56.8 ± 2.7	44.2 ± 1.9	67.2 ± 3.4
10 µM NS5806	51.7 ± 1.8 (5)*	101 ± 6.2 (8)***	22.6 ± 0.7 (6)*	68.1 ± 3.8 (10)*	43.5 ± 1.5 (11)	83.2 ± 4.7 (9)***
Area (µA·ms–1) control	814 ± 70	2260 ± 181	66 ± 9.8	378 ± 74	762 ± 63.9	1450 ± 103
10 µM NS5806	1250 ± 109 (5)**	3150 ± 166 (8)***	67 ± 10 (6)	533 ± 101 (10)**	825 ± 84 (11)	1890 ± 142 (8)**
V1/2 (mV) control	−60.8 ± 0.85	−44.7 ± 0.7	−65.2 ± 1.1	−57.3 ± 0.9	−55.4 ± 0.5	−48.6 ± 0.4
10 µM NS5806	−75 ± 1.8 (5)***	−59.5 ± 0.5 (8)***	−75.7 ± 1.9 (6)***	−67.1 ± 1.3 (10)***	−66.0 ± 1.0 (10)***	−54.0 ± 1.1 (8)**
Recovery τ (ms) control	80.8 ± 3.5	8.0 ± 2.8	110 ± 29	12.6 ± 3.0	95.8 ± 2	15.9 ± 0.5
10 µM NS5806	205 ± 31 (5)***	37.1 ± 10 (8)***	202 ± 54 (6)**	26.4 ± 1.8 (10)***	221 ± 8 (8)***	23.7 ± 0.48 (8)***

K_V4 channels expressed with and without KChIP2 (1:1 molar ratio) in Xenopus laevis oocytes. Currents were activated from a holding potential of −100 mV by a +40 mV step before and during application of 10 µM NS5806 and peak current amplitudes, time constants (τ) of current decay and total charge movement for the first 150 ms after complete activation was measured. Steady-state mid-inactivation (V_1/2) was evaluated from a holding potential of −100 mV by a series of 2 s prepulses from −100 to +40 mV followed by a +40 mV step. Boltzmann equations were fitted to normalized tail current amplitudes plotted as a function of the prepulse potential. Time constants (τ) for recovery from inactivation was determined by a two-pulse protocol; from a holding potential of −80 mV currents were activated by two test potentials to +40 mV with increasing interpulse time. The peak current at the second pulse was normalized to the first pulse and single exponential functions were fitted to the data points. The different K_V4 α-subunits were recorded on different days; however, the experiments in absence and presence of KChIP2 were performed in parallel and thus current amplitude and biophysical characteristics can be directly compared.

^*P < 0.05,

^**P < 0.01

^***P < 0.001; significantly different in the absence and presence of NS5806.

KChIP2, K channel interacting protein 2.