Fig. 1. ( A ) Mean force transients induced by the optical isomers and racemates of ropivacaine and bupivacaine, respectively, in concentrations of 1, 5, 10, and 15 mm. All force transients are normalized to maximum force transient at 24.9 μm Ca2+. * P < 0.05 versus R -isomer in identical concentrations; § P < 0.05 versus corresponding ropivacaine isomers/racemate in identical concentrations. n = 6 fiber bundle preparations per agents at each concentration. ( B ) Transformation of force transients induced by tested local anesthetics ( fig. 1A ) into corresponding Ca2+transients, based on the individual [Ca2+]–force relation of each fiber. * P < 0.05 versus R -isomer in identical concentrations; § P < 0.05 versus corresponding ropivacaine isomers/racemate in identical concentrations. n = 6 fiber bundle preparations per agents at each concentration. BUP = bupivacaine; ROP = ropivacaine.