Rundown kinetics of recombinant human and murine 5-HT_3A receptors after multiple activation.

<p>(A) Representative current traces for human (left) and murine (right) receptors showing currents after the first and 26^th application of 5-HT. Records were obtained from the same cell. (B) Repeated 5-HT applications (26 applications within 40 min) reduced peak currents (left) and charge (right) through H123 (filled circles) and M<i>123</i> (open circles) differently. Since rundown affects plateau currents and desensitization of H123 more effectively than those of M<i>123</i>, the calculation of charge thus represents a very sensitive parameter for receptor activity. (C) Bar diagram showing the change in plateau currents, t_des1 and t_des2 after 22 to 26 5-HT applications (mean ± SEM). Values were normalized to current kinetics evoked by the first application of 5-HT.