Values are mean ± SEM (n = 6 to 12) of the integrated values of luminescence in ROI of the tibial cranial muscle 3 days after electrotransfer of 3 μg of pC1 luc plasmid as measured in vivo after luciferin injection i.p. (2.5 mg/250 μl, n = 6 or 6 mg/250 μl, n = 6) or locally (0.1 mg/40 μl n = 12). Local injection of luciferin was performed 2 hours or more after the i.p. injection. Background luminescence was subtracted from the luminescence measured.