Fig. 2. Competitive inhibition of mosapride on the 5-hydroxytryptamine type 3 (5-HT₃) receptor currents.

(A) Representative traces of 5-HT₃ receptor currents induced by 1, 3, 10, 30 µM 5-HT in the presence (black traces) or absence of 10 µM of mosapride (gray traces), near IC₅₀ seen in Fig. 1B. The open horizontal bars indicate the drug application period. (B) Averaged concentration-response curve of 5-HT₃ receptor currents in the presence (●) or absence (○) of mosapride. The data were normalized to the peak amplitude induced by 10 µM 5-HT and lines were obtained by fitting these data to equation (1) in the Methods. The EC₅₀ of 5-HT was increased from 1.88 ± 0.10 µM (n = 10) to 4.80 ± 0.32 µM (n = 8) by mosapride (p < 0.001, unpaired t-test) without Hill coefficient changes. There were no significant differences in the peak amplitudes induced by 30 µM 5-HT alone and the co-application of mosapride with 30 µM 5-HT (p = 0.7282, unpaired t-test). The data are expressed as means ± standard error of the mean.