Acid-sensing ion channels (ASICs) are proton-gated ion channels which are highly sensitive to extracellular acidosis and are permeable to cations1, predominantly Na+. To date, six different ASIC subunits (1a, 1b, 2a, 2b, 3 and 4) encoded by four genes have been identified. Three subunits assemble to form homomeric or heteromeric channels which are expressed throughout the CNS and PNS. Excitatory ASIC channels have a proposed role in nociception and pain, and other neurological diseases such as ischaemia, inflammation and learning and memory.