Fig. 3.

Pretreatment with chloride channel blockers attenuates the initiation of an acetylcholine (ACh) contraction in guinea pig tracheal rings. A: representative tracing of tension recordings in organ bath with guinea pig tracheal rings contracted with ACh EC₅₀ dose. Tracheal rings treated with vehicle show no attenuation of contraction, whereas pretreatment with compound 13 100 μM plus bumetanide 10 μM for 15 min shows attenuation of the initiation of contraction. B: pretreatment with a combination of chloride channel blockers plus bumetanide attenuated the initiation of an ACh contraction, whereas treatment with chloride channel blockers or bumetanide alone failed to attenuate the initiation of ACh contractions. Compound 1 100 μM/bumetanide 10 μM: 48.9% ± 3.6; compound 13 100 μM/bumetanide 10 μM: 37.5% ± 5.8; NPPB 100 μM/bumetanide 10 μM: 41.5% ± 6.3. ***P < 0.001 compared with vehicle; n = 5. Muscle force calculated as a percent of first ACh EC₅₀ contraction.