Figure 2.

Effect of a pretreatment with 3 µM erythromycin on I_hERG block by terfenadine (a) and thioridazine (b). Left panels show representative current traces for effects of 100 nM terfenadine (ai) or 100 nM thioridazine (bi) on I_hERG after a 15‐min preincubation with 3 µM erythromycin. Currents were elicited using the protocol shown in the lower panels. Right panels show isochronal concentration–response relationships for terfenadine inhibition of I_hERG (aii) or thioridazine (bii) in the presence of 3 µM erythromycin. Fit to the concentration–response curves yielded an IC₅₀ of 4 nM ((CI 0.63–25.6 nM); n = 5 cells per concentration) for terfenadine and 46.4 nM ((CI 36.3–59.3 nM); n = 4 to 6 cells per concentration) for thioridazine. Respective n_H were of 0.30 (CI 0.14–0.47) for terfenadine and of 0.73 (CI 0.58–0.90) for thioridazine. Asterisks in Aii denote statistical significance: ** at p < .01 and *p at < .05 (two‐way ANOVA with Bonferroni post hoc test)