Figure 6.

ORK1 currents in oocytes are blocked by barium but not TEA. (a) Current–voltage relationship with constant perfusion of 20 mM KCl solution containing 0 mM (▿), 0.3 mM (○), or 1 mM (•) barium chloride by the protocol in Fig. 4a (mean ± SEM, n = 3 cells). (b) Current–voltage relationship with constant perfusion of 20 mM KCl solution with 0 mM (▿), 2.5 mM (○), or 25 mM (•) TEA chloride isotonically substituted for NaCl (mean ± SEM, n = 3 cells). (c) ORK1-induced currents in an oocyte perfused with 20 mM KCl solution in the absence (control) or presence of 1 mM barium chloride by the protocol in Fig. 4a. Scale bars represent 2 μA and 15 ms. (d) Voltage dependence of barium block was assessed by measurements of conductance from −150 mV to −75 mV in the presence of 0.3 mM (○) or 1 mM (•) barium chloride by the protocol in Fig. 4a. The data shown are from one oocyte but are representative. G_o and G are the cord conductances measured in the absence and presence of barium, respectively. The electrical distance was calculated from K_i(V) = K_i(0)exp(zδFV/RT), where K_i(0) is the zero voltage inhibition constant, z is the valence of the blocking ion, and δ is the fraction of the applied voltage drop experienced at the binding site (36).