It has been generally accepted that Cisapride (Prepulsid® or propulsid®), a widely used gastrointestinal prokinetic agent, is associated with Torsades de Points, a life-threatening arrhythmia. Recently, cisapride-induced APD (action potential duration)-prolongation was inhibited by glibenclamide, a K_ATP channel blocker. But the direct effect of cisapride on K_ATP channels has not been studied until now. Therefore, we investigated cisapride's effects on K_ATP channels of isolated rat ventricular myocytes.

After the isolation of rat ventricular myocytes, we analysed the single channel current with patch pipettes. The method of analysis was the student t-test.

1) Cisapride (10^-6 M-10^-4 M) inhibited K_ATP channel opening without changing channel conductance Ki was about 20µM, and Hill coefficient was 0.75. 2) Cisapride inhibited pinacidil-induced K_ATP channel opening in the cell attached mode.

These results suggest that cisapride-induced APD prolongation and arrythmic effects may be partly related to K_ATP channel inhibition.