Fig. 5.

La³⁺ reversibly blocked channel activity. We found that 1 mm La³⁺blocked all conductances completely within seconds. Block by micromolar concentrations of La³⁺ was much slower.A, Current activity is shown before the application of the blocker. The all-points current histogram (right) was generated from the sample data (left). TheP_(open) shown in the top right corner of the histogram plot is the averageP_(open) calculated from the data shown on the left. Calculations ofP_(open) were made as described in Materials and Methods. B, Example of the activity seen during the application of 10 μm LaCl₃. The application of LaCl₃ occurred at the beginning of the trace and continued through the entire trace. C, Data are shown for a patch exposed to 1 mm LaCl₃, after which activity was almost completely blocked. D,Activity that began to recover several seconds after we removed LaCl₃. V_hold = −20 mV.