Potential-dependent inhibition of cardiac Ca2+ inward currents by Ro 40-5967 and verapamil: relation to negative inotropy.

Ro 40-5967 is a structurally novel Ca2+ channel blocker which binds to the [3H]desmethoxyverapamil receptor in cardiac membranes with a potency similar to that of verapamil but which has considerably fewer negative inotropic effects. In the present study, the inward Ca2+ current was measured in isolated myocytes with the whole-cell patch-clamp technique. It was found that at a physiological membrane potential (-80 mV) Ro 40-5967 was also less potent than verapamil in inhibiting this current, and that negative inotropy and Ca2+ channel blockade were correlated.