[(A), upper panel] Concentration-dependent inhibition of tetrodotoxin-resistant (TTX-r) Nav1.8 by isoflurane. Current traces of TTX-r Nav1.8 are shown in the absence or presence of two isoflurane concentrations. Normalized peak INa values for TTX-r Nav1.8 were fitted to the Hill equation to yield IC50 values and Hill slopes (Herold et al., 2009). [(A), lower panel] Effects of isoflurane on NaChBac expressed in HEK293 cells. Families of current traces are shown at two different holding potentials (Vh) in the absence or presence of isoflurane. Isoflurane significantly inhibited INa from a Vh of either −80 or −100 mV (Ouyang et al., 2007). (B) Inhibition of Nav1.4 by equipotent concentrations of various inhaled anesthetics. Peak INa were recorded from a holding potential of –80 mV by 25-ms test steps as shown in the inset. The effects of clinically equipotent concentrations of halothane, isoflurane, sevoflurane, enflurane, and desflurane are shown in these representative traces. Desflurane had the greatest effect of peak INa reduction.