Figure 2.

Dantrolene does not affect steady-state inactivation of the fast skeletal muscle Na⁺ current. Representative recordings of skeletal Na⁺ current elicited by 20 ms depolarizations to 0 mV immediately following 300 ms prepulses ranging from −110 mV to −10 mV are shown for untreated control myotubes (a) and myotubes exposed to 10 μM Dantrolene (b). The voltage protocol is not drawn to scale. (c) Voltage-dependence of inactivation for control (⚫; n = 11) and Dantrolene-treated (⚪; n = 8) myotubes. Inactivation was fit by (4) (see Section 2) with the following respective parameters for control and Dantrolene treated groups: V _1/2 inact = −44.3 ± 1.6 and −41.2 ± 1.1 mV; k = −8.4 ± 0.9 and −7.7 ± 0.3 mV. Inactivation curves are superimposed with activation curves shown in Figure 1 to illustrate window current.