Figure 4.
(A) Steady-state inactivation was determined from a holding potential of −160 mV by using a series of 300-ms prepulses from −160 to +27.5 mV in 7.5-mV increments before the test pulse to −20 mV. Note that all measurements were performed in chloride-reduced pipette solution containing fluoride and yielding highly negative Vh0.5. (B) Voltage dependence of time constants of fast inactivation time constants, τh, is given for both mutants and WT (n = 6–9). (C) Recovery from inactivation for a holding potential of −120 mV was determined by a 100-ms depolarization to −20 mV followed by a variable-duration return to −120 mV. (D) Representative action potentials from a muscle fiber segment of the HypoPP6 patient compared to those of a normal control. They were elicited from various holding potentials by a short depolarizing pulse. Note the slower rise and fall for HypoPP.