Figure 4.

Nicotine peak current and net charge responses. A) Nicotine peak current concentration-response curves. The β4–6–α3 concatamer was co-expressed at a 1:5 RNA ratio with either α3, β4, β2, or α5. Data were initially normalized to 100 µM ACh control responses obtained immediately prior to the test responses and subsequently adjusted to the empirically determined ACh maximum responses. B) Nicotine net-charge concentration-response curves. The β4–6–α3 concatamer was co-expressed at a 1:5 RNA ratio with either α3, β4, β2, or α5. Data were initially normalized to 100 µM ACh control responses obtained immediately prior to the test responses and subsequently adjusted to the empirically determined ACh maximum responses. C) The ratio of net charge to peak current (relative to 100 µM ACh controls) for nicotine-evoked responses. A–C Data for progressive increases in nicotine concentration were used from a single experiment only under conditions when ACh controls remained of stable amplitude throughout each experiment. In some cases, nicotine applications prevented the full recovery of ACh controls; in those cases, responses evoked by nicotine relative to ACh were determined in a series of single concentration experiments using new sets of cells for each nicotine concentration. All points represent the average data (± SEM) for at least four cells.