Fig. 5.

Activation and inactivation of the slow delayed rectifier K⁺ current component. A,B, Traces of K⁺ current obtained by subtraction in BC patches (I_{0.5 mm4-AP} − I_{0.5 mm 4-AP + 20 mm TEA} in A, I_{1 mm TEA} − I_{20 mmTEA} in B). C, Activation curves for BC patches (open circles, n = 9) and PC patches (filled circles,n = 9). Data points were fitted with Boltzmann functions raised to the fourth power. D, Steady-state inactivation curves for BC patches (open circles,n = 9) and PC patches (filled circles, n = 10); 10 sec prepulses. Data points were fitted with sum of a Boltzmann function and a constant.E, 20–80% rise time, plotted against test pulse voltage for BC patches (open circles,n = 9) and PC patches (filled circles, n = 9). F, Deactivation time course at −40 mV in a BC patch. Top traces represent I_{0.5 mm4-AP}, and I_{0.5 mm 4-AP + 20 mm TEA}, bottom trace represents subtracted current. Note the slow deactivation (decay τ 21.6 msec). Pulse programs identical to those used for Figure 4. For curve parameters, see Table 1.