Fig. 1.

Chloride channel blockers relax a tetraethylammonium chloride (TEA) contraction in guinea pig tracheal rings. A: structures of compounds 1 and 13. B: representative tracing of muscle force recordings in organ bath with guinea pig tracheal rings contracted with 10 mM TEA. Rings were treated with vehicle or compounds. Compound 1 completely relaxed TEA contraction within 15 min. C: 100 μM compound 1 and compound 13 relaxed a TEA contraction (23.8 ± 14.9, 61.0 ± 10.1, respectively, calculated as percent of remaining TEA contraction at 15 min). **P < 0.01, ***P < 0.001 compared with vehicle; n = 6–9.