Figure 6.

Representative examples of outside-out patches containing single ASIC2-3 channels activated by increasing concentrations of external protons, pH_o 6.0, 5.0, and 4.0. Activity of the channel and P_o increase with increasing [H⁺]_o. At pH_o 6.0, the openings are short and are separated by closed events of variable duration, some of which last several hundred milliseconds. At pH_o 5.0, the short openings increase in frequency and longer openings are apparent. At pH_o 4.0, there is a further increase in P_o due to long openings. The closed and open levels are indicated on the right side. O_S, O_I, and O_L indicate short, intermediate and long open states, respectively. C_S and C_L indicate short and long closed states, respectively. Bath solution contained 150 mM Na⁺, and pipet solution contained 140 mM K⁺. Membrane potential was held at −60 mV. The data were recorded at 5 kHz and filtered at 1 kHz for display. The bars on the bottom indicate the time and amplitude scales in pA and seconds, respectively.