Figure 7.

Effects of Ba²⁺ on astrocyte passive conductance and cloned TWIK-1 and TREK-1 K⁺ channels. A, B, Representative whole-cell current traces recorded from TWIK-1 (A) and TREK-1 (B). K⁺ channels expressed in CHO cells induced by voltage ramp pulses before (black lines) and after (gray lines) bath application of 800 μm Ba²⁺. The washout recording traces (dashed lines) are superimposable with the control traces. C, Dose–response curves of Ba²⁺ blockade of TWIK-1 (open squares) K⁺ channels. The continuous line is a fit of Equation 3, yielding an IC₅₀ of 960 ± 9.8 μm with h = 0.84. Blockade of astrocyte passive conductance (filled circle) and TREK-1 (filled square) K⁺ channels at test voltage 20 mV by 1.2 mm Ba²⁺ and 800 μm Ba²⁺, respectively, are also shown (n = 5–7 for each data point). D, Representative traces of whole-cell currents recorded from an astrocyte before and after application of 1.2 mm Ba²⁺ in bath solution. E, The mean current–voltage relationships for the representative recordings shown in D (n = 6). Calibration: 10 ms and 2 nA.