A, I–V curves show the activation of TREK-1 by halothane (0.53 mm) under hypoxia. B, voltage-clamp currents (•) (at –50 mV, derived from standard voltage ramps) showing that the activation of TREK-1 by halothane (Hal, 0.53 mm) was comparable under normoxia (20% atm oxygen) and hypoxia (3% atm oxygen). Halothane was transiently applied as indicated by the filled bars. C, summary of the effects of halothane (0.53 mm) on TREK-1 currents under normoxia and hypoxia from whole-cell recordings at –50 mV. Halothane activated TREK-1 under normoxia and hypoxia by 42 ± 4% and 43 ± 8% (means ± s.e.m.; n = 6), respectively.