Fig. 4.

Chloride channel blockers relax the maintenance phase of a preestablished ACh contraction in guinea pig tracheal rings. A: representative tracing of tension recordings of guinea pig tracheal rings contracted with an ACh EC₅₀ dose. Treatment with vehicle (0.1% ethanol and 0.1% DMSO) showed no relaxation, whereas treatment with compound 13 100 μM and bumetanide 10 μM alone showed relaxation within 30 min. B: treatment with chloride channel blockers, bumetanide, or the combination relaxed an ACh contraction. Compound 13 (60.1% ± 5.7) relaxation was significantly increased when combined with bumetanide (27.3% ± 5.6) (calculated as percent of remaining ACh EC₅₀ contraction at 30 min). *P < 0.05, **P < 0.01, ***P < 0.001 compared with vehicle; #P < 0.05 compared with compound 13 alone; n = 5–8.