Figure 5.

Skeletal L-type Ca²⁺ currents are little affected by Dantrolene in the absence of RyR1. Representative current families evoked from −80 mV to 0, 10, 20, 30, and 40 mV for dyspedic myotubes treated with DMSO vehicle (a) or 10 μM Dantrolene (b) for >10 minutes at ~25°C. In the case of the latter, the step from −80 mV to 0 mV evoked some T-type current visible at the beginning of the pulse. Peak I-V relationships are shown in (c). Smooth I-V curves were fit by (1) (see “Section 2”) with the following respective parameters for control (n = 8) and Dantrolene-treated (n = 14) groups: G _max⁡ = 57 ± 6 and 43 ± 5 nS/nF; V _1/2 = 36.6 ± 4.5 and 28.1 ± 2.2 mV; k = 10.9 ± 1.6 and 11.8 ± 2.0 mV. No significant (P > 0.05, unpaired t-test) differences were observed amongst the fit parameters. (d) Comparison of conductance-voltage relationships for control and Dantrolene-treated dyspedic myotubes. The average conductance values (derived from I-V data using (2); see Section 2). (e) Inactivation summary. R ₂₀₀ = fraction of the peak current remaining at the end of the 200 ms test depolarization to +30 mV.