From the ‡Institute of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences,

Acid-sensing ion channels (ASICs) are ligand-gated cation channels activated by extracellular protons. In periphery, they contribute to sensory transmission, in-cluding that of nociception and pain. Here we charac-terized ASIC-like currents in dorsal horn neurons of the rat spinal cord and their functional modulation in path-ological conditions. Reverse transcriptase-nested PCR and Western blotting showed that three ASIC isoforms, ASIC1a, ASIC2a, and ASIC2b, are expressed at a high level in dorsal horn neurons. Electrophysiological and pharmacological properties of the proton-gated cur-rents suggest that homomeric ASIC1a and/or hetero-meric ASIC1a 2b channels are responsible for the pro-ton-induced currents in the majority of dorsal horn neurons. Acidification-induced action potentials i