Figure 2.

Volatile anesthetics inhibit Na⁺ channels in various expression systems. [(A), upper panel] Electrophysiological recordings of isolated rat neurohypophysial nerve terminals show a reversible block of Na⁺ currents and [(A), lower panel] action potentials evoked by small current injections at clinically relevant concentrations of isoflurane (Ouyang et al., 2003; Ouyang and Hemmings, 2005). (B) Effects of isoflurane on channel recovery from fast-inactivation of three different Na⁺ channel isoforms heterologously expressed in mammalian cells. Recovery was assessed using a two-pulse protocol with a 30-ms conditioning pulse followed by a variable recovery interval of up to 30 ms, and then a 5-ms test pulse to peak activation voltages. The time course of channel recovery from fast-inactivation was well fitted by a monoexponential function [(B), left panels]. Representative current traces for a holding potential (V_h) of −100 mV are shown for all three subtypes [(B), right panels; Ouyang and Hemmings, 2007].