Figure 9.

Intracellular acidification enhances tachyphylaxis A, top, ASIC1a was repeatedly activated by pH 6; conditioning pH was pH 7.3. In the experimental group, during the 60 s intervals, 90 mm ${\text{NaHCO}}_3^{-}$ was applied to acidify the intracellular compartment. Bottom, current amplitudes were normalized to the first amplitude. Continuous lines represent fits to a single exponential function. n = 13 for the control group, n = 11 for the experimental group. **P < 0.001 by t test. B, top, ASIC1a was repeatedly activated by pH 5. In the experimental group, 90 mm ${\text{NaHCO}}_3^{-}$ was applied for 5 min. Bottom, relative current amplitudes, normalized to the first amplitude, are shown as bars. The first amplitude after ${\text{HCO}}_3^{-}$ incubation (‘3^rd application’) was not smaller than in the control group. n = 11 for the control group, n = 10 for the experimental group.