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. Author manuscript; available in PMC: 2018 Oct 1.
Published in final edited form as: Eur Biophys J. 2017 Jul 10;46(7):617–626. doi: 10.1007/s00249-017-1239-1

Fig. 5.

Fig. 5

Isoflurane inhibition of eukaryotic and prokaryotic Nav. a Macroscopic whole-cell Na+ current traces recorded from a mammalian ND7/23 cell endogenously expressing tetrodotoxin-sensitive Nav in the absence (gray discontinued traces) or presence (purple traces) of 0.8 mM isoflurane (~2.5 MAC). From a holding potential (Vh) of −80 mV the alternating stimulation protocols were chosen to test voltage-dependent inhibition. A test pulse (10 ms at 0 mV) to elicit peak Na+ current was preceded by a 300-ms prepulse to either −130 mV (denoted “V0”; left traces) or to a voltage at which approximately half of the channels were in the fast-inactivated state (denoted V½; –70 mV; right traces). b Steady-state inactivation (or Na+ channel availability; h∞) of tetrodotoxin-sensitive Na+ currents (Nav1.4) was tested using a double-pulse protocol with a 30-ms prepulse of from −110 to −20 mV in 10-mV steps, followed by a 25-ms test pulse to −10 mV. Peak Na+ current was normalized (INa/INamax), plotted against prepulse potential, and fitted with a two-state Boltzmann distribution to calculate V½, which was shifted by −10 mV in the presence of 0.8 mM isoflurane. Data are expressed as mean ± SD, n=7. Adapted from (Ouyang et al. 2009). c NaChBac current traces recorded from a transfected HEK293FT cell in the absence (gray discontinued traces) or presence (purple traces) of 0.8 mM isoflurane (~2.5 MAC) using the stimulation protocols depicted from a Vh of either −140 mV or −80 mV to test for voltage-dependent inhibition. The time scale over which NaChBac activates and inactivates is considerably slower than for mammalian Nav (~500 ms vs. 2–3 ms, respectively); the accelerated NaChBac current decay in the presence of isoflurane is also noteworthy. d NaChBac steady-state inactivation was tested from a Vh of −140 mV with 90-s prepulses ranging from −140 to −40 mV followed by a test pulse to −10 mV. V½ was shifted by −16 mV in the presence of 0.8 mM isoflurane. Data expressed as mean ± SD, n = 7–15. Adapted from (Sand et al. 2017).