Figure 4 A) The effect of halothane concentration on I-V curves of mean peak and end-pulse IBa normalised to control IBa(max) and showing S.E.M. as vertical bars. For each trial halothane was introduced successively at 1% (), 2% (◇ ) and 4% (△), interspersed by washes of 2-3 minutes which reversed the effects completely (control ). IBa(max) was monitored throughout and pulse I−V protocols performed during the plateau of maximal response to the drug. B) Normalised means of IBa(max) for peak and end-pulse currents are plotted against percentage volatile anaesthetic concentration for halothane (), isoflurane (◇) and sevoflurane (). Vertical bars indicate s.e.m. where n = 6 for halothane and n = 7 for isoflurane and sevoflurane. C) Normalised means of IBa(max) for peak () and end-pulse () currents plotted against pentobarbitone concentration. Linear regressions are fitted though each dose-response plot in 4B and 4C using the least squares method. All have an R2 value greater than 099.
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