Properties of the inward-rectifying K+ channel Kir7.1 expressed in rat choroid plexus epithelial cells. A) Current -voltage relationships with extracellular K+ of 5, 50 or 145 mM. The current-voltage relationships were produced by applying 0.8 s ramp potentials from Vm = -160 to 40 mV. B) Kir reversal potentials (Erev) as a function of extracellular K+ activity ([K+]o). Erev was measured in experiments similar to those in A (n = 3). The line through the data was predicted by the Nernst equation for a conductance which is perfectly selective for K+. Figure reproduced with permission from Kotera and Brown .