Changes in Fluo-5N fluorescence induced by depolarization in control and in mdx fibers. (A) Means and SEM of Fluo-5N fluorescence changes in response to depolarizing pulses to −10, +10, and +30 mV from a holding potential of −80 mV in 12 control (C57BL6 mice; left) and 11 mdx (right) fibers. Images were collected at a frequency of 12.5 Hz. (B) Relationship between the mean changes in Fluo-5N fluorescence and membrane potential in control and mdx fibers. The changes in Fluo-5N fluorescence were measured as explained in the legend of Fig. 4. (C) Mean percentages of fluorescence recovery 1 s after the end of the depolarizing pulses at +10, +20, +30, and +40 mV in the 12 control and 11 mdx fibers. Mean values have been compared using a Student’s unpaired t test. Error bars indicate mean ± SEM.