Immunocytochemical localization of ASIC3 in rat sensory neurons. A, ASIC3 antibody labeled COS-7 cells transfected with ASIC3 (top), but not those transfected with ASIC1a (bottom). It also failed to label cells transfected with ASIC1b and ASIC2a (not shown); ASIC2b and ASIC4 were not tested. B, ASIC3 immunoreactivity in a section of L5 DRG. Less than half of neurons are labeled and no non-neurons are labeled. Note the presence of both small and large labeled neurons (inset). Scale bar, 40 μm. C, Size-frequency distribution of ASIC3-positive neurons (black) and of all neurons (grey) from the L5 DRG. ASIC3+ cells are present in all size bins. 3345 neurons (12–15 sections from 3 rats) were counted, of which 1359 (40%) were ASIC3-positive.