For many years it has been observed that extracellular acid activates transient cation currents in large-diameter mechanosensory dorsal root ganglion (DRG) neurons. However, the molecular basis of these currents has not been known. Large DRG neurons express the dorsal root acid sensing ion channel (DRASIC), suggesting that DRASIC might contribute to H+-gated DRG currents. To test this, we exami...