Figure 4. A rise in [K⁺]_o slows the inactivation of erg channels.

A, representative current traces evoked by test pulses to potentials between −80 and +60 mV following a 2 s depolarizing pulse to +20 mV with a subsequent 25 ms hyperpolarization to −100 mV (for erg1 and erg2) or −60 mV (for erg3) in cells expressing erg1, erg2 or erg3 channels. The holding potential was −20 mV. Vertical and horizontal scale bars denote 1 nA and 100 ms. B, mean time constants of inactivation (τ_inact) as a function of the test pulse potential for the three erg channels determined in 2 mm K⁺ and after a change to 10 mm K⁺ solution. C, voltage dependence of the ratio of the steady-state current to the maximal erg current at the onset of inactivation. *P≤ 0.05 and **P≤ 0.01, significant differences with two-tailed paired t test. The insets show the voltage dependence of the extrapolated instantaneous current (I_max) in the two different [K⁺]_o concentrations. Filled symbols, 2 mm[K⁺]_o; open symbols, 10 mm[K⁺]_o.