CLCN1 and Myotonia: In contrast, addition of verapamil to the bath did not recover the fixed component of weakness in ClC-1–/– or CaV1.1Δe29 ClC-1–/– muscles, as shown by non-normalized force plots in Supplemental Figure 6, C and D. Next, we determined the impact of CaV1.1Δe29 conductance on transient weakness in the setting of pharmacologic inhibition of ClC-1, where the long-term adaptive response of skeletal muscle to myotonia has not occurred (26).