EFFECTS OF 3,6-DIMETHYLAMINO-DIBENZOPYRIODONIUM FORMIATE ON ACTION POTENTIAL AND SLOW INWARD CALCIUM CURRENT IN ISOLATED GUINEA PIG VENTRICULAR MYOCYTES

The effects of 3, 6-dimethylamino-dibenzopyriodonium formiate (IHC-64) on action potential and slow inward calcium current (I_si) were investigated in isolated guinea pig ventricular myocytes using whole cell voltage clamp recording. IHC-64 (20 and 200 μmol/L) was shown to markedly decrease APD₂₀ and APD₉₀. However, in the presence of nisoldipine, no obvious effects of IHC-64 on APD₂₀ could be detected. Under voltage clamp conditions, IHC-64 (20 and 200 μmol/L) caused a significant decrease in I_si. The results indicate that IHC-64 can block the calcium channels in isolated guinea pig ventricular myocytes.