Figure 4. Single BK_Ca channel blockade by TEA.

A, recording from an outside-out patch in control solution at 0 mV containing one channel. The corresponding point amplitude histogram is plotted below the recording. N, number of events. B, same patch in the presence of 0.5 mm TEA. The histogram showed an apparent reduction of amplitude by 53 %. The effects of all TEA concentrations tested were reversible. Pipette solution, high-${\text{K}}_{\text{i}}^{\text{+}}$, pCa 4; bath solution, control-Hepes; filter frequency, 2 kHz. C, data from measurements at 0 mV obtained as shown in B at different TEA concentrations. Fit of the data points by eqn (2) revealed a half-maximum inhibitory concentration (IC₅₀) of 0.40 ± 0.04 mm, with a Hill factor of 0.98 ± 0.09 (n = 5–30).