Fig. 7. Non-stationary noise analysis of macroscopic tail currents is shown. (A ) Averaged tail currents recorded from macropatches in response to a repolarization to −140 mV after completion of a 1-s positive pulse to 40 mV. The traces are averages of 150 records before (control) and after perfusion of 1.5% halothane to the bath (halothane), which resulted in an approximate decrease in current of 38.5% measured at the peak of the tail current. (B ) Averaged ensemble variance of the experiment shown in A . Variance computed by pairs. 24(C ) Sample variance as a function of mean current. The continuous curves represent data fits to the equation ς2= iI − I2/N (Materials and Methods section). The fits yielded the indicated values for the single-channel current and number of channels. Data were filtered at 10 kHz. Pipette: 120 KMS; bath: 120 KMS.