Fig. 3. Effects of volatile anesthetics on K+currents through charybdotoxin-sensitive Ca2+-activated K+(KCa) channels (IK(Ca)) and 4-aminopyridine–sensitive delayed rectifier K+(KDR) channels (IK(DR)) in tracheal and bronchial smooth muscle cells. (A ) Effect of 1.5 minimum alveolar concentration (MAC) isoflurane on the IK(Ca)recorded in a bath solution containing 5 mm 4-aminopyridine by depolarizing pulses from a holding potential of −70 to +60 mV in a tracheal smooth muscle cell (top ). Relative IK(Ca)–voltage relations obtained before and after exposure to volatile anesthetics in tracheal and bronchial smooth muscle cells (bottom ). (B ) Effect of 1.5 MAC sevoflurane on the IK(DR)recorded in a bath solution containing 100 nm charybdotoxin by depolarizing pulses from a holding potential of −70 to +60 mV in a bronchial smooth muscle cell (top ). Relative IK(DR)–voltage relations obtained before and after exposure to volatile anesthetics in tracheal and bronchial smooth muscle cells (bottom ). Data are expressed as mean ± SD (n = 7 each). *P < 0.05 versus control.