A, I–V curves show no modulation by hypoxia (2% atm oxygen) of the TREK-1 current activated by an internal pH of 6.6. B, voltage-clamp currents (•) (at –50 mV, derived from standard voltage ramps) showing that hypoxia had no effect on the TREK-1 current after activation by an internal pH of 6.6. C, I–V curves show the inhibition of TREK-1 during alkalinization by ammonium chloride (10 mm) under hypoxia. D, voltage-clamp currents (•) (at –50 mV, derived from standard voltage ramps) showing that the inhibition of TREK-1 by ammonium chloride (10 mm) was comparable under normoxia (22 ± 0.4% atm oxygen) and hypoxia (2 ± 0.1% atm oxygen). Ammonium chloride was transiently applied as indicated by the filled bars.