Fig. 1.
NS9283 potentiates single-channel currents through (α4)3(β2)2 AChRs. a BOSC 23 cells transfected with a tenfold excess of α4 over β2 subunit cDNAs predominantly express (α4)3(β2)2 AChRs. Amplitude histogram from a cell-attached patch recording in the presence of 10 μM ACh reveals a single conductance class of channel openings with 4.1 pA unitary current amplitude (holding potential − 70 mV). b Single-channel currents were recorded with 10 μM ACh in the recording pipette (holding potential − 70 mV; Gaussian filter 4 kHz). Left panel shows a closed duration histogram fitted by the sum of exponentials. The point of intersection of adjacent components (arrow) yields a critical closed time τcrit of 0.7 ms. Center panel shows a histogram of channel openings separated by closings longer than τcrit fitted by the sum of three exponential components (dashed curves); an exemplar channel opening is shown. Right panel shows a histogram of channel openings separated by closings briefer than τcrit; an exemplar channel opening episode is shown. c Single-channel currents were recorded in the presence of 10 μM ACh and 10 μM NS9283 as in b. Left panel shows a closed duration histogram fitted by the sum of exponentials. The point of intersection of adjacent components (arrow) yields a critical closed time τcrit of 30 ms that was used to distinguish episodes of un-potentiated from potentiated channel openings. Closed duration components that selectively flank potentiated channel openings are shaded. Middle panel shows a histogram of channel openings separated by closings longer than τcrit; exemplar channel openings are shown. Right panel shows a histogram of channel openings separated by closings briefer than τcrit; exemplar channel opening episodes are shown. Exponential components corresponding to potentiated openings are shaded. Percentage of channel openings that are potentiated is indicated by the shaded portion of the bar. d Panel summarizes the classes of channel opening episodes recorded in the presence of ACh without (left traces) or with NS9283 (right traces)