Fig. 4. Responses of IK patches to sodium gluconate and halothane. Sodium gluconate (A  and B ) and halothane (C  and D ) were applied via  a piezo-driven fast application system to inside-out (A  and C ) and outside-out (B  and D ) patches of oocytes expressing IK. Currents were measured at +100 mV (A  and C ) and −100 mV (B  and D ) in the presence of 10 μm Ca²⁺. The time scale represents 100 ms (bars ). To facilitate the comparison, inward currents were shown upward in B  and C .