Figure 5.

Single channels underlying the inward currents. A, Representative traces with unitary currents from an outside-out extensor patch bathed in solution (b) during steps (arrows) to the indicated membrane potentials, lasting 5 s. The inter-pulse-interval was 30 s. Solutions: (b)/(f). Note the downward deflections signifying channel opening. B, An average of 10 traces of current evoked by a repeated step to −170 mV in the patch of A. Note the gradually increasing inward current similar to the time-dependent whole-cell current in Figure 1A. The dash at the left indicates the closed-channel current. C and D, The same patch as in A, now bathed in solution (e). Note the similar pattern of activity (as in A and B). Pipette solution: (f). E, Single-channel activity at −110 mV (left), and a corresponding all-points amplitude histogram presented at the same current scale (right), to illustrate the complicated multilevel appearance of the unitary events. Dotted line and C, the closed-channels current level. Solutions: (c)/(f).