Figure 3.

Influence of nAChR subunit loop domains upon single-channel conductance. Chimaeric subunits containing the M3–M4 intracellular loop domain from the α3 subunit (a), α8 subunit (b) or α10 subunit (c) were expressed in tsA201 cells and analysed by whole-cell recording. Representative whole-cell responses were obtained by a 20-s application (thick horizontal scale bar) of 50 μM DMPP (left panel). Vertical scale bars=100 pA. Below each whole-cell response is shown a high-gain band-pass filtered (2 Hz–2 kHz) record illustrating the increase in noise variance associated with each response. Vertical scale bars=10 pA. Representative plots illustrating the noise power spectrum (right panel) for each chimaera are also shown. Estimates of channel conductance were derived from both noise spectral analysis and plots of variance against mean current of 5–9 cells. Conductance estimates are presented here as a mean from both types of analysis with standard errors. DMPP, 1,1-dimethyl-4-phenylpiperazinium iodide; nAChR, nicotinic acetylcholine receptor.