Fig. 7.
Effects of isoflurane and halothane on recovery of Nav1.4 from fast inactivation. The protocol, shown in the upper right inset, involved 12 depolarizing test steps at various recovery times (t) in 2.5 ms intervals. Representative current traces obtained for the effects of isoflurane (~2.3 MAC) and halothane (~2.2 MAC) are shown on the right. The time course of channel recovery from fast inactivation was best fitted by a mono-exponential function in all cases to yield a recovery time constant (τr). The rate of recovery, expressed as current normalized to initial control current, was slowed by isoflurane (A) and halothane (B). The recovery time constant was greater for halothane than for isoflurane at the higher concentrations as determined by sum-of-squares F-test between curve fits of mean data (P < 0.001). Mean isoflurane concentrations were 0.44±0.06 mM and 0.82±0.08 mM; mean halothane concentrations were 0.41±0.07 mM and 0.78±0.10 mM. Data are expressed as mean±SEM, n=5–8. *** P < 0.001 vs. control.