Rabbit Ventricular Myocytes

A voltage-clamp analysis of the effect of almokalant on the delayed rectifier K' current (IK) was made in rabbit ventricular myocytes. The two-suction pipette method was used, and appropriate voltage-clamp protocols were used to study more specifically use dependence, block development, and recovery from block. Almokalant interacted with the IK in two ways: it shifted the activation curve in the hyperpolarizing direction (stimulatory effect) and blocked the open lK channel in a use-dependent way (inhibitory effect). For 2-second voltage clamps to +20 mV, half-maximum block was obtained at 5 x 10-8 mol/L, with a Hill coefficient of 1.76. Use-dependent block was related to an open-channel block that occurred at 0 mV with a time constant of 1.07 second and a rather slow recovery from block. at -50 mV, recovery time constant