The effects of elevated [Na+]i or high [K+]e on Leu-209 mutant channel activity. (A) I–Vt relationships for oocytes expressing either wt (n = 5) or mutant Slo2.1 channels (L209A, n = 4; L209N, n = 4; L209E, n = 7). Currents were recorded immediately after impalement of an oocyte with 2M NaCl-containing electrodes (control), after maximum response to intracellular Na+ loading and again after addition of 1 mM NFA to the extracellular solution. (B) I–Vt relationships for wt (n = 6), L209A (n = 3), L209N (n = 4) and L209E (n = 7) Slo2.1 channels measured from oocytes bathed in K104 extracellular solution in the absence (control) and presence of 1 and 6 mM NFA. Error bars indicate ± S.E.