Figure 7. Gating properties of the A-type K⁺ current component.

A, traces of K⁺ current in the presence of 20 mm external TEA. Pulse protocols (identical to those used in Fig. 5) are shown above the traces. B, activation curve (•, n = 10) and steady-state inactivation curve (○, n = 7). C, 20–80 % rise time, plotted against test pulse potential (n = 10). D, decay τ, plotted against test pulse potential (n = 10). The decay phase of the current during a 100 ms pulse was fitted with the sum of a single exponential function and a constant. E, traces of K⁺ currents in the presence of 20 mm external TEA. Pulse protocol: holding potential −90 mV, 150 ms pulse to +70 mV (conditioning pulse), pulse of variable duration to −90 mV, 150 ms pulse to +70 mV (test pulse), and step back to −90 mV. Pulse protocol is shown above the traces. F, time course of recovery from inactivation (n = 6). The amplitude of the peak current evoked by the test pulse (I₂) divided by that evoked by the conditioning pulse (I₁) was plotted against the interpulse interval. Data points were fitted with the sum of two exponentials. For curve parameters see Table 1.