Proton concentration dependent slowing of the capsaicin deactivation rate. Two applications of capsaicin were interrupted by 5 s applications of external solutions with increasing proton concentrations. A) Representative current traces. The deactivation rate was slowed slightly by mildly acidic solutions that did not activate the channel directly but that potentiated the capsaicin response (pH 7.0 and 6.8). The slowing of the capsaicin deactivation rate was enhanced even more by application of acid that could directly activate the channel (pH 6.0 and 5.5). B) Concentration-dependent effects of pH on the deactivation-time constant of capsaicin. C) No concentration dependent effects were recorded for the deactivation rate of the second capsaicin application, indicating that previous exposure to acidic conditions does not affect subsequent capsaicin deactivation.