Figure 1.

Currents of homomeric ASIC1a exhibit tachyphylaxis A, representative examples of currents from homomeric ASIC1a, -1b, -2a and –3, and from heteromeric –1a/3 and –1a/2a. ASICs were repeatedly activated by application of pH 5 (pH 4.5 for ASIC2a) for 10 s. Channels were allowed to recover in conditioning pH 7.4 for 60 s. The measurements with ASIC1a/ASIC3 were done in the presence of 40 nm PcTx1 (see Methods). Bars correspond to 60 s and 2 μA, respectively. B, current amplitudes were normalized to the first amplitude. The depression of the ASIC1a current amplitude could be well fitted with a single exponential function (continuous line). ASIC1a, n = 10; ASIC1b, n = 6; ASIC2a, n = 7; ASIC3, n = 7; ASIC1a/3, n = 7; ASIC1a/2a, n = 9. C, ASIC1a was repeatedly activated as in A, but the conditioning pH was pH 8.0. n = 11.