Figure 2.

Barium sensitivity. (A) Percentage inhibition of steady-state K_ir current vs. [Ba²⁺]o. [K⁺]_o = 2.5 mM, 32°C. The data (green dots) were fitted with a logistic function (see text), giving a concentration at half-block (Kd) of 0.21 ± 0.10 mM, and a slope (Hill coefficient) of 0.69 ± 0.23 (n = 5, −120 mV). (B,C): sample tracings obtained in a single cells in response to hyperpolarizing steps from −40 to −120 mV in standard saline plus BL1 and BL2 (B), and in the presence of 1 mM Ba²⁺ (C). (D,E): same experimental conditions and protocol as above; blocking effect of 1 mM Cs⁺. (F) Voltage dependence of the blocking time constant; the data points were obtained in the presence of 1 mM Ba²⁺ (yellow dots) or Cs⁺ (orange dots).