A, a representative example of the inhibition of IK,O2 by acidic pH in symmetrical 135 mm K+ solutions. Acidosis (pH 6.4 and 5.5) caused ∼50 % inhibition of IK,O2 at negative potentials. B, normalised pH sensitivity of IK,O2 in GPN neurones and TASK-1 current expressed in COS-7 cells (data from Kim et al. 1999) at −60 mV in symmetrical K+ solutions. Note the weak pH sensitivity of IK,O2 expressed in GPN neurones compared to TASK-1 current.