Acid-sensing ion channels (ASICs) are Na⁺ channels activated by external protons. The ASIC family includes four members: ASIC1, ASIC2, ASIC3 and ASIC4. The ASIC family is in fact part of a large channel superfamily known as degenerin/epithelial Na⁺ channels (DEG/ENaC) and share the same basic characteristics: two transmembrane spanning domains, a large extracellular domain and short intracellular N- and C- termini.