PT - JOURNAL ARTICLE AU - M P Davies AU - L C Freeman AU - R S Kass TI - Dual actions of the novel class III antiarrhythmic drug NE-10064 on delayed potassium channel currents in guinea pig ventricular and sinoatrial node cells. DP - 1996 Mar 01 TA - Journal of Pharmacology and Experimental Therapeutics PG - 1149--1154 VI - 276 IP - 3 4099 - http://jpet.aspetjournals.org/content/276/3/1149.short 4100 - http://jpet.aspetjournals.org/content/276/3/1149.full SO - J Pharmacol Exp Ther1996 Mar 01; 276 AB - We have investigated the concentration-dependent modulation, by the novel class III antiarrhythmic compound NE-10064, of the delayed potassium channel current Iks in isolated guinea pig sinoatrial nodal (SAN) and ventricular cells. At concentrations greater than 1 micron, the drug potently inhibited Iks in each of the cell types investigated. The concentration-dependent inhibition of Iks (IC50 = 700 nM) was the same in ventricular and SAN cells. At near-threshold drug concentrations, we also observed increases of Iks activity in both SAN and ventricular cells. The NE-10064-induced enhancement of Iks was more pronounced at voltages near the Iks activation threshold (0 mV), than at more positive voltages in both cell types. Furthermore, the agonistic effects of the drug were more prominent before steady-state effects of the compound were attained, which suggests parallel agonistic and antagonistic pathways. Our results demonstrate that Iks channels in cells of the sinoatrial node region of the guinea pig heart respond to NE-10064 in the same manner as cells of the ventricle and that this compound, although a potent inhibitor of Iks activity, possesses an interesting but as yet mechanistically unidentified agonistic action at low concentrations in both cell types.