Figure 11. I-V relationships for I_DA.

A and B, voltage protocols and superimposed current traces recorded in the same cultured HISM cell using high-Cs⁺ pipette and high-K⁺, divalent cation-free external solution in which I_Na is abolished and I_DA can be measured. I_HA was relatively small in this cell: measured by applying voltage ramps from −40 mV to inactivate I_DA, I_HA amplitude was −427 pA at −70 mV and 315 pA at +60 mV. In B steps were in the range −70 to +60mV. Tail current was flat at +20 mV. C, I-V relationships for the peak I_DA in A (•) and instantaneous tail current amplitude in B (○), measured as described for Fig. 10B. Tail current reversed at +23 mV which was 3 mV more positive than the peak I_DA reversal potential. This discrepancy could arise as a result of some contamination of the peak I_DA by I_HA, as explained above, for which V_rev 0 mV.