Fig. 7. Effects of quinidine on ventilation frequency in adult zebrafish. (A) Zebrafish were exposed to 0.1 mmol l^–1, 0.5 mmol l^–1 and 1 mmol l^–1 quinidine in a continuously perfused chamber. Bars represent the duration of quinidine application at each concentration. While 0.1 mmol l^–1 quinidine had no effect, the addition of 0.5 mmol l^–1 and 1 mmol l^–1 significantly increased (asterisks) ventilation frequency (min^–1; mean ± S.E.M.) compared to the control (N=6; P<0.05; ANOVA–Bonferroni test). This effect was fully reversible. (B) Dose–response curve of data in A. Data points from 2, 5, 8 and 11 min are plotted. Asterisks indicate a significant increase from control (0 mmol l^–1). N=6; P<0.05; ANOVA–Bonferroni test.