Dibenzylamine - a novel blocker of the voltage-dependent K+ current in myocardial mouse cells

Ventricular myocytes of the mouse ventricle were voltage clamped with a pat ch-clamp technique in the whole-cell configuration. At depolarizing voltage pulses, these myocytes develop a large voltage-dependent K+ outward curren t. Application of the drug dibenzylamine (DBA) to the bath solution blocked the voltage-dependent K+ current. The concentration/response relationship for the peak current at +40 mV indicates a 1:1 binding of the drug to the r eceptor with a concentration of half maximum effect of 43.1 mu mol/l. The b lock did not require activation of the channels by depolarizing pulses. At concentrations causing partial block (25 mu mol/l), the block was independe nt of voltage. At the same concentration, DBA completely blocked the slow c omponent of the recovery from inactivation (-80 mV) whereas steady-state in activation was not altered. It is concluded that DBA is a novel blocker of the voltage-dependent K+ current in mouse cardiac myocytes which preferenti ally affects the current component generating the slow recovery from inacti vation.