We have examined slow inactivation of L-type calcium current in canine Purkinje myocytes with the whole cell patch clamp technique. Slow inactivation is voltage dependent. It is negligible at -50 mV but can inactivate more than half of available iCaL at -10 mV. There are two major consequences of this slow inactivation. First, standard protocols for the measurement of T-type current can dramati...
