Effect of MDL-12,330A and/or SNAP on sildenafil-induced relaxation on carbachol-induced human detrusor contraction. Concentration–response curves to sildenafil or vehicle were performed in the presence of MDL-12,330A (10 µM; N = 17) or SNAP (10 µM; N = 9) or their combination (N = 6), or their respective vehicle (N = 20) on carbachol (1 µM)-induced detrusor contraction. Results are expressed as the net effect of sildenafil where the effect of its vehicle has been subtracted. The data are mean ± SEM of N bladders. Vehicle versus MDL-12.330A: ###P < 0.001, two-way anova followed by a modified post hoc Student's t-test with the Bonferroni adjustment for multiple comparisons *P < 0.05, ***P < 0.001 at the concentrations shown MDL-12.330A versus MDL-12.330A + SNAP: & & &P < 0.001, two-way anova.