Figure 6. α-BgTx blocks the 18 pS nAChR channels.

Cell-attached single channel opening elicited by ACh (2.5 μM) with or without α-BgTx (500 μM) included in the patch pipette. The neurones have been incubated with α-BgTx for ≥ 15 min prior to recording. The opening probability of the 18 pS channel is significantly reduced when α-BgTx is included in the patch pipette (n = 7). The records shown here were obtained from ‘α5 minus’ neurones as the contribution of the 18 pS channels is significantly increased under these conditions (see accompanying paper, Yu & Role, 1998). Identical results were obtained from recordings of control neurones. A, sample scatter plots of all channel openings in a typical patch recording with ACh ± α-BgTx in the patch pipette. Each point represents an individual opening at the amplitude indicated on the y axis; openings of the 18 pS conductance range are delineated by dotted lines. With α-BgTx in the pipette, the number of openings of this class of channels is significantly reduced. B, open probability of the 18 pS channel is plotted as a function of time. The P_o of the 18 pS channel is greatly reduced in the presence of α-BgTx.