Data analysis and statistics.

MiniAnalysis software (Synaptosoft, Decatur, GA) was used to analyze the DSM phasic contraction parameters. The DSM contractile activity was quantified from measurement of average phasic contraction amplitude (the difference between the force-time baseline curve and the maximum peak of the contractions), frequency (contractions/min), muscle force integral (calculated by integrating the area under the force-time baseline curve), phasic contraction duration (defined as width of the individual phasic contraction at 50% of the amplitude), and DSM tone (the difference between the zero line and the force-time baseline curve). Statistical analyses were performed with Prism 4.03 software (GraphPad, La Jolla, CA), and CorelDRAW Graphics Suite X3 software (Corel, Ottawa, ON, Canada) was used to illustrate the data. For the EFS-induced contractions, the contraction amplitude at the EFS frequency under control conditions was taken to be 100%, and the data were normalized. For evaluation of the effect of cumulative addition of 9-phenanthrol (0.1–30 μM) on 10-Hz EFS-induced contractions, the last 5 min before addition of each concentration to the bath were analyzed. The TICCs were analyzed as NP_o, as previously described (39, 44). In voltage step experiments, the last 200-ms interval was analyzed and averaged before, after, and following washout of 9-phenanthrol. Five minutes of ≥10 min of stable current-clamp recordings prior to application of 9-phenanthrol were analyzed for control data, and the last 5 min of each 10-min continuous recording after application of 9-phenanthrol were analyzed to evaluate the effect of 9-phenanthrol on the membrane potential. Data are summarized as means ± SE for the number of DSM strips or cells (n) isolated from the number of patients (N). Data were compared using a two-way ANOVA followed by Bonferroni's post test or paired or unpaired Student's t-test where appropriate. P < 0.05 was considered statistically significant.