Current decay of myotonia mutant channels.
The time constant of decay is altered in hNaV1.4F1705I compared to wild type hNaV1.4 channels. (A) Superimposed normalized currents through wild type and hNaV1.4F1705I channels at test pulses of −30, −20, and −10 mV exhibiting slowing of current decay in the mutant channel. (B) The time constants of current decay of hNaV1.4F1705I channels are significantly different compared to wild type in the absence (p<0.05) or presence of 0.5 µM of Ca2+ (p<0.001). The inset is an expanded view −20 mV to 0 mV. (C) Raw current traces of hNaV1.4F1705I channels at RT and at 37°C. Currents were measured at −20 mV, in the same cell at different temperatures with 0.5 µM of Ca2+ in the pipette. (D) Plot of the time constants of current decay of wild type and hNaV1.4F1705I channels at RT and at 37°C in 0.5 µM of Ca2+. Paired measurements were made at RT and at 37°C. The current decay of hNaV1.4F1705I is significantly different at 37°C compared to RT (p<0.05). (E) Plot of the steady-state inactivation of hNaV1.4F1705I channels at 37°C in 0.5 µM of Ca2+. For comparison the steady-state inactivation of wild type and hNaV1.4F1705I from Figure 1E are re-plotted. The symbols are the same in plots B, D and E.