Fig. 6.
Effects of isoflurane, halothane and desflurane on voltage dependence of Nav1.4 fast inactivation. A. Representative traces show inhibition of INa by isoflurane (left), halothane (middle) and desflurane (right) using a fast inactivation protocol (inset) involving a conditioning pulse of 30 ms followed by a test pulse of 25 ms to minimize slow inactivation. Normalized data were fitted to the Boltzmann equation to yield voltage of 50% inactivation (V1/2in) and slope factor for ~1 MAC (B) or ~2 MAC (C). Each anesthetic significantly shifted the V1/2in in the negative direction as determined by sum-of-squares F-test comparison between curve fits of mean data (P < 0.05). Parameters derived from analysis of independent curve fits are presented in Table 1. Anesthetic concentrations were 0.46±0.09 mM and 0.82±0.07 mM for isoflurane; 0.40±0.06 mM and 0.77±0.10 mM for halothane; and 0.82±0.06 mM and 1.61±0.07 mM for desflurane. Data expressed as mean±SEM, n=5–7.