Figure 1. Spatially averaged Ca²⁺ transients elicited by an AP in EDL fibres from C57BL/10 mice.

A, normal fibre; B, mdx fibre. In each panel, the upper trace shows the furaptra ΔF/F_R response elicited by a supra-threshold external shock initiated at 0 time. The fluorescence excitation and emission wavelengths were 410 ± 20 nm and > 470 nm, respectively; F_R was corrected for a small non-furaptra-related component of intensity. Six individual responses were averaged in A and four in B; the waiting time between successive shocks was 3 min. In A, the Ringer soultion contained 5 μm BTS; thus, this trace is likely to be virtually free of movement artifacts. In B, BTS was not used; thus this trace may be contaminated with a small movement artifact beginning 10–15 ms after stimulation. The lower panels show Δ[Ca²⁺] calculated from ΔF/F_R with eqns (1) and (2). Fibre diameters, 42 μm and 39 μm; sarcomere length, 3.8 μm and 3.5 μm; furaptra concentration, 30 and 85 μm.