Action potential (APs) and Oregon Green BAPTA-5N (OGB-5N) transients recorded from WT, mdx, and utr−/−/mdx fibers. A: superimposed APs recorded from WT (solid trace), mdx (dashed trace), and utr−/−/mdx (dotted trace) fibers in response to a single pulse of stimulation. AP peak (mV) and full duration at half-maximum (FDHM, in ms) were 128 and 2.46; 123 and 2.73; and 123 and 3.9 for the WT, mdx, and utr−/−/mdx fiber, respectively. B: typical OGB-5N transients elicited by single AP in WT (solid trace), mdx (dashed trace), and utr−/−/mdx (dotted trace) fibers. ΔF/F peak and FDHM (in ms) of OGB-5N transients were 0.75 and 1.68; 0.50 and 1.8; and 0.52 and 1.5; for the WT, mdx, and utr−/−/mdx fiber, respectively.