Fig. 7.

Chronic incubation with DHβE increases the frequency of opening at 100 nm ACh. A, Typical single-channel currents recorded in an outside-out patch pulled from a control cell (left) or pulled from a cell incubated for 22 hr in 10 μm DHβE (right). The horizontal bars indicate pulses of ACh. Each trace is the first record of multiple sweeps (16 for the control cell and 17 for the 10 μm DHβE-treated cell). B, Average single-channel currents confirm the increase observed for whole-cell currents after DHβE-induced upregulation. Unitary currents including those presented inA were average for a control patch (left; mean of 10 sweeps) or for a patch pulled from a cell exposed for 22 hr to 10 μm DHβE (right; mean of 10 sweeps). C, Cumulative all-point amplitude histograms corresponding to multiple sweeps including and after the ones presented in A (16 sweeps in control and 17 sweeps for 10 μm DHβE). Surface areas of the Gaussians for channel openings and setup noise have values of 99 and 1703 (in control) and 288 and 1344 (in 10 μm DHβE). The open time probabilities are of 5.8% (control) and of 21.4% (10 μm DHβE) for these two representative patches.