Figure 8.

Al³⁺-induced currents through an outside-out patch. (a) Current at three levels of V_m. The arrows indicate transitions in current of magnitude greater than that between individual levels. Broken lines show closed state of the channel. (b) Current–voltage curves obtained from mean amplitude histograms of the current amplitudes. A current–voltage curve obtained from a voltage ramp is superimposed. (c) Current–voltage curves obtained from voltage ramps in 20 mM and 2 mM TEACl. Pipette solution (mM): 100 TEACl, 2 EGTA, 10 Hepes, and 7 TEAOH to pH 7.2. The external solution consisted of 20 mM TEACl, 0.2 mM CaCl₂, and 50 μM Al³⁺, pH 4, for the high-Cl⁻ solution and 2 mM TEACl, 0.2 mM CaCl₂, and 25 μM Al³⁺, pH 4, for the low-Cl⁻ solution. The activity of free Al³⁺ cations was 13.5 μM in both solutions.