Figure 5. Characterization of Kv1.1 cloned from canine colon tissue.

A, representative currents recorded from an oocyte injected with cRNA encoding Kv1.1. Currents were evoked by 400 ms voltage steps from a holding potential of -80 mV to test potentials ranging from -80 to +50 mV, followed by a step to -40 mV to measure tail currents. B, normalized Kv1.1 tail currents at -40 mV following 400 ms step to test potentials ranging from -80 to +50 mV were fitted with a Boltzmann function (V_1/2= -25.0 mV, k = 7.7 mV, n = 5). C, voltage dependence of inactivation of Kv1.1 current was measured using 15.5 s conditioning pulses from -70 to +20 mV followed by a step to +40 mV. Normalized test currents were plotted as a function of conditioning pulse potential and fitted with a Boltzmann function (V_1/2= -44.8 mV, k = 4.4 mV, n = 6). D, dose-response relationship for DTX-K was plotted at steady-state block. The IC₅₀ was 0.34 nm for DTX-K (n = 5). The inset shows illustrative Kv1.1 currents evoked by 400 ms voltage steps from a holding potential of -80 mV to 0 mV in the absence (○) and presence (⋄) of 1 nm DTX-K.