Kinetics of acid-activated currents in HEK293 cells stably expressing rat TRPV1 channels. Application of solutions with increasing proton concentrations to cells voltage-clamped at -60 mV result in progressively larger inward currents with slightly slower activation and deactivation rates. (a) Representative current traces. (b) pH response curve of average normalized currents. (c) Plot of average activation and deactivation rates as a function of pH. In contrast to the activation rates, which are similar between capsaicin and acid, the deactivation rates of acid responses are much faster than the capsaicin responses. Data are the mean ± SEM.