Figure 3.

Regional differences in Ca²⁺-independent, depolarization-activated K⁺ currents in isolated adult mouse left ventricular myocytes. Outward K⁺ currents were recorded as described in Fig. 1 during 4.5-s depolarizing voltage steps to potentials between −40 and +60 mV from a holding potential of −70 mV; the records displayed are from three different cells: one isolated from the apex (A) and the other two from the septum (B and C). As is evident, peak outward current amplitudes in A are substantially larger than those in B and C. In addition, the decay phases of the outward K⁺ currents in C are slower than those in A or B and the rapidly inactivating transient K⁺ current, I_to,f that is so prominent in A is not evident in the records in C (see text). Scale bars, 2 nA and 500 ms.