Fig. 6.
E-4031–sensitive rapidly activating delayed rectifier K+ current (IKr) in the absence and presence of desflurane in sinoatrial node cells. (A) Superimposed current traces during 250-ms depolarizing steps to −10 mV applied from a holding potential of −50 mV, under control conditions (a), after 5 min exposure to 12% desflurane (DES; b), and 5 min after the subsequent addition of 5 μM E-4031 (c). (B) IKr in control (a–c), derived by digital subtraction of the current trace in the presence of desflurane and E-4031 (c) from that in their absence (a), shown in A. IKr in the presence of 12% desflurane (b–c), obtained by digitally subtracting the current trace in the presence of desflurane and E-4031 (c) from that in the presence of desflurane alone (b). The tail current (dotted points) was fitted with a single exponential function (continuous curve) with a time constant (τ) as indicated in this example. (C) Current–voltage relationships for IKr tail currents, determined as E-4031–sensitive difference currents in the absence and presence of 6 and 12% desflurane. The smooth curves through the data points represent the least-squares fit of the Boltzmann equation. (D) The maximal amplitude of IKr (IKr,max) in control and in the presence of desflurane at 6 and 12%, obtained by Boltzmann fits.