Dantrolene inhibits skeletal L-type Ca²⁺ currents. Recordings of L-type currents elicited by 200-ms depolarizations from −50 mV to the indicated test potentials are shown for an untreated normal myotube (A) or a normal myotube exposed to 10 μM dantrolene for >10 min at ∼25°C (B). (C) Comparison of I-V relationships for untreated (•; n = 10) and dantrolene-treated myotubes (○; n = 12). Currents were evoked at 0.1 Hz in 10-mV increments after a prepulse protocol (see Materials and methods). Current amplitudes were normalized by linear cell capacitance (pA/pF). The smooth curves are plotted according to Eq. 1, with best-fit parameters presented in Table I.