Mean open channel lifetimes of currents from multiple channel currents and single channel currents. The currents were recorded from Xenopus oocytes at -120 mV in divalent free perfusion solutions and were sampled at 20 kHz and filtered at 5 kHz. (A) Single channel current (left) shown with the idealized current above and the histogram below. The mean amplitude and open channel noise are 4.1 pA and 2.4 pA. (B) Currents from a patch containing two channels (left) with the idealized currents shown above and the histograms below. The mean amplitude and open channel noise are 4.8 pA and 1.5 pA. (C) Mean open lifetimes of currents from patches containing one (n = 6), and two (n = 4) and three (n = 5) opening levels. (D) The relative open channel noise of single channel currents and of the 1st and 2nd opening levels of multiple channel currents. The amplitude difference between 1st and 2nd level of multiple channel currents is insignificant. However, the noise of multiple channels (either 1st or 2nd level) and single channel currents is significantly different (p > 0.05, t-test).