875755-24-1

NS 8593 is an inhibitory gating modifier of small-conductance calcium-activated potassium (K_Ca2/SK) channels (K_ds = 0.42, 0.6, and 0.73 μM for K_Ca2.1/SK1, K_Ca2.2/SK2, and K_Ca2.3/SK3, respectively, in the presence of calcium) that decreases the calcium sensitivity of SK channels. It is selective for K_Ca2/SK channels over intermediate- (K_Ca3.1/IK_Ca1) and large-conductance (BK) potassium channels at 10 μM. NS 8593 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). It inhibits aerosolized acetylcholine chloride-induced increases in respiratory system resistance in mice when administered as an aerosol at a dose of 500 μM. NS 8593 (5 mg/kg) decreases the duration of burst-pacing-induced atrial fibrillation in normotensive and spontaneously hypertensive rats.

The compound (R)-N-(benzimidazol-2-yl)-1,2,3,4-tetrahydro-1-naphtylamine (NS8593) reversibly inhibited recombinant SK3-mediated currents (human and rat SK3) with potencies around 100 nM. NS8593 did not inhibit 125I-apamin binding. NS8593 decreased the calcium sensitivity by shifting the activation curve for Ca2+ to the right, only slightly affecting the maximal Ca2+-activated SK current. NS8593 inhibited all the SK1-3 subtypes Ca2+-dependently (Kd = 0.42, 0.60, and 0.73 μM, respectively, at 0.5 μM Ca2+. NS8593 did not affect the calcium-activated potassium channels of intermediate and large conductance (hIK and hBK channels, respectively). NS8593-mediated inhibition was prevented in the presence of a high concentration of the positive modulator NS309.

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[1] DORTE STR?BAEK. Inhibitory gating modulation of small conductance Ca2+-activated K+ channels by the synthetic compound (R)-N-(benzimidazol-2-yl)-1,2,3,4-tetrahydro-1-naphtylamine (NS8593) reduces afterhyperpolarizing current in hippocampal CA1 neurons.[J]. Molecular Pharmacology, 2006, 70 5: 1771-1782. DOI: 10.1124/mol.106.027110
[2] BEI-BEI LIU . NS8593 inhibits Ca2+ permeant channels reversing mouse airway smooth muscle contraction[J]. Life sciences, 2019, 238: Article 116953. DOI: 10.1016/j.lfs.2019.116953
[3] JONAS G DINESS. Effects on atrial fibrillation in aged hypertensive rats by Ca(2+)-activated K(+) channel inhibition.[J]. Hypertension, 2011, 57 6: 1129-1135. DOI: 10.1161/hypertensionaha.111.170613