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. Author manuscript; available in PMC: 2010 Aug 27.
Published in final edited form as: P R Health Sci J. 2010 Mar;29(1):4–17.

Figure 3.

Figure 3

Single-channel analysis of wild-type mouse and δS268F acetylcholine receptor. A) Current-voltage relationships for single-channel currents recorded from wild-type (WT) (open squares) or δS268F-acetylcholine receptor (AChR) (open circles) expressed in X. laevis oocytes. B) WT mouse and δS268F AChR single-channel currents recorded at low acetylcholine (ACh) concentration. AChR single-channel currents recorded from cell-attached patches on X. laevis oocytes expressing WT AChR (left) and AChRs expressing the δS268F mutation (right). All channels were recorded at a holding potential of 100 mV, 4 μM ACh, filtered at 5 kHz, sampling rate at 20 μsec per point and temperature of 22°C. Openings are shown as downward deflections, with close state denoted by the c, and the open state denoted by o. Representative histograms for current amplitude and open time distributions are shown for each of the AChR tested. Amplitude histograms were constructed from events list files created to include all event amplitudes that could be detected. The resulting distribution data was fitted with a Gaussian function with the appropriate number of components. Both the WT and mutant AChR show a single amplitude component of 7.874 ± 0.883 pA and 7.371 ± 0.465 pA, respectively. Open time histograms were fitted with exponential functions of the appropriate number of components using the maximum likelihood algorithm. The WT AChR shows two open time constants: τo1 = 0.411 msec (f = 0.229) and τo2 = 1.435 (f = 0.711), while the δS268F AChR shows two open time components of τo1 = 0.826 msec (f = 0.164) and τo2 = 10.582 msec (f = 0.896). Data were filtered at 5 kHz for each current sample display. Scale values are 5 pA for the vertical bar and 10 msec for the horizontal bar. C) Kinetics of activation of WT and δS268F AChR at high ACh concentrations. (Left) Single-channel currents elicited by the indicated concentration of ACh recorded from cell-attached patches from X. laevis oocytes expressing adult mouse AChRs containing the WT δ (upper) or mutated δS268F (lower) subunit. Recordings were done at holding potential of 100 mV, filtered at 5 kHz, sampling rate at 20 μsec per point and temperature of 22°C. Channel openings are shown as downward deflections. (Center and right) Open and closed time duration histograms for adult mouse AChRs containing the WT δ (upper) or mutated δS268F (lower) subunits generated and fitted using pSTAT6. Fitting was done using the simplex least-squares algorithm. Single-channel currents displayed were filtered at 4 kHz. (Figure 3 is reproduced by permission from Gómez et al. (2002) Annals of Neurology 51: 102–112).