Coexpression of CaM (E/Q) leads to quick rundown of SK current. (A) Representative current traces recorded under voltage clamp with an inside-out patch excised from a Xenopus oocyte injected with RNA for SK channels and CaM (E1Q). Voltage protocol is shown on top. For clarity, only one trace recorded at the beginning of each minute after patch excision is shown. Horizontal dashed lines in this and other figures represent zero current level. (B) Average current level at −80 mV measured every 3 s from the same patch in A is plotted as a function of time. The jump in current at the beginning of the time course in this and later figures indicates patch excision. Data points during solution change were noisy and removed from the plot in this and other figures. Solid line represents a single-exponential fit of the time course with τ = 108 s. (C) Representative current traces recorded and shown as in A with a patch excised from an oocyte injected with RNA for CaM (WT) and SK channels. Note a small shift in the reversible potential during the course of recording. (D) Average current level at −80 mV from the patch shown in C measured and plotted as in B.