Prolonged exposure of TRPV1 to acidic pH produces a time-dependent change in the deactivation rate of capsaicin-activated currents. Single pulse protocols were used to determine time dependent differences in the deactivation of capsaicin currents following prolonged exposure to acidic pH. A) Co-application of acid (pH 5.5) and capsaicin produced sustained currents independent of the duration of application. TRPV1 channels were activated by 1 μM capsaicin for 4 s, followed by 8 seconds of capsaicin + pH 5.5. The time dependence (1–8 s) of the sustained current is shown below and illustrates the reproducibility of the responses, the lack of desensitization and the parallel deactivation time-courses. B) Deactivation time constant of capsaicin response is decreased if acidic conditions persist after capsaicin application is terminated. Note the slow decline in current amplitude following removal of capsaicin, and the relatively faster deactivation rates of deactivation with longer intervals of acid pH application, presumably due to fast deactivating acid responses (see figure 2) contributing a greater proportion of the total current.