Fig. 6.

AHR caused a left-shift in steady-state inactivation curve without affecting voltage-dependence and kinetics of activation. a Steady-state inactivation experiments were performed in cells treated with and without 50 μM AHR. In these experiments, a dual-pulse protocol was used in which a test pulse step of +70 mV was preceded by a long pre-pulse (20 s) of different potentials. The test pulse currents were normalized to the largest test pulse current and plotted against the pre-pulse voltages. The curves are fitted with the Boltzmann equation. Results are means ± SEM from three to five cells of each group. b Voltage-dependence of activation: Kv currents were stimulated with increasing depolarization (from a holding potential of −70 mV and then 10 mV increments), and conductance (G) is calculated as described in "Materials and methods". Conductances in the control group and the AHR (50 μM)-treated groups are normalized with their respective maximum conductance (G _max) and then plotted against the applied depolarization voltages. The curves are fitted with the Boltzmann equation. Results are means ± SEM from 3 to 4 cells of each group. c The recordings of two different cells are shown, illustrating early current kinetics (+30 mV stimulation) in the absence and presence of 50 μM AHR. Similar results were obtained in at least nine more experiments. d Results from (c) were quantified. Activation time constants were obtained by an exponential fit to the rising phase of the currents. Results are means ± SEM from ten cells of each group