Current Recorded From the Rabbit Basilar Artery

Actions ofFRC8653 on the macroscopic and unitary Ba2` currents were studied using the rabbit basilar artery. Application of (+)-FRC8653 (<1 ,uM) increased the amplitude of the inward current when depolarization pulses more negative than -10 mV were applied but inhibited it when depolarization was more positive than 0 mV (in each case from a holding potential of -80 mV). At a holding potential of -40 mV, (-)-FRC8653 (>0.1 nM) consistently inhibited the inward current. (-)-FRC8653 (>1 nM) inhibited the amplitude of the inward current evoked by a depolarizing pulse more positive than -10 mV (the holding potential being -80 mV). At the holding potential of -80 mV, but not at -40 mV, (+)-FRC8653 (1 ,uM) enhanced the current amplitude evoked by a depolarizing pulse more negative than -10 mV but inhibited the current evoked by a pulse more positive than 0 mV. (-+-)-FRC8653 shifted the voltage-dependent inhibition curves to the left, and the slope of the curve became steeper (test pulse of + 10 mV).