Depression of ACh-evoked currents through human and mouse muscle wild-type AChRs. (A) Example current trace recorded from an outside-out patch containing human muscle wild-type AChRs exposed to a 50-Hz train of 0.8-ms ACh pulses (100 µM). The train of pulses is indicated above the current recording. (B) Peak-current values in response to the applied 50-Hz trains were normalized with respect to the first peak in each series and averaged across replicate experiments (six for the mouse AChR and seven for the human counterpart). Vertical error bars are standard errors. The orange circles superimposed on the human AChR data points correspond to the fit from which the estimate of the rate of recovery from desensitization within a train of ACh pulses was obtained (see Materials and methods). The corresponding fit to the mouse AChR data points is shown in Fig. 5.