An inhibitory gating modifier of SK channels (Kds = 0.42, 0.6, and 0.73 μM for SK1, SK2, and SK3, respectively, in the presence of calcium); decreases the calcium sensitivity of SK channels; selective for SK channels over IK and BK potassium channels at 10 μM; induces relaxation of potassium- or acetylcholine chloride-precontracted isolated tracheal rings from wild-type mice (IC50s = 8.9 and 39.8 μM, respectively) or from mice in an ovalbumin-induced model of allergic asthma (IC50s = 16.4 and 32.2 μM, respectively); inhibits aerosolized acetylcholine chloride-induced increases in respiratory system resistance in mice when administered as an aerosol at 500 μM; decreases the duration of burst-pacing-induced atrial fibrillation in normotensive and spontaneously hypertensive rats at 5 mg/kg