Permeating protons contribute to tachyphylaxis of the acid-sensing ion channel (ASIC) 1a

The homomeric acid-sensing ion channel 1a (ASIC1a) is a H + -activated ion channel with important physiological functions and pathophysiological impact in the central nervous system. Here we show that homomeric ASIC1a is distinguished from other ASICs by a reduced response to successive acid stimulations. Such a reduced response is called tachyphylaxis. We show that tachyphylaxis depends on H + permeating through ASIC1a, that tachyphylaxis is attenuated by extracellular Ca 2+ , and that tachyphylaxis is probably linked to Ca 2+ permeability of ASIC1a. Moreover, we provide evidence that tachyphylaxis is probably due to a long-lived inactive state of ASIC1a. A deeper understanding of ASIC1a tachyphylaxis may lead to pharmacological control of ASIC1a activity that could be of potential benefit for the treatment of stroke.