Figure 5. Dynamic action potential clamp with WT or Y1795C I_Na.

A, subepicardial cell APs elicited at 1 Hz before and after a 2 s pause. APs with mutant I_Na are prolonged compared to WT (see Table 1). B, boxed APs from A and associated I_Na in C, on expanded time scale. HEK cell I_Nas were scaled to identical peak amplitudes (21 nA), and applied to the ‘subepicardial’ PB model cell as an external current input. Note that late I_Na-increase after the pause is more pronounced with the mutant (^*). Broken line shows zero current level; peak I_Na is off scale; note the slower time-course of peak I_Na-inactivation of the mutant compared to the WT (arrows). D, relationship between the APs from B and selected membrane current components of the PB model cell, showing the changes in the time-course of transient outward K⁺ current (I_to), slowly and rapidly activating components of the delayed rectifier K⁺ current (I_Ks and I_Kr, respectively), and L-type Ca²⁺ current (I_Ca), along with changes in mutant I_Na.