Acid-sensing ion channel-lb in the stereocilia of mammalian cochlear hair cells

We investigated whether amiloride-blockable proton-gated cation channels ASICIa (acid-sensing ion channel-la) and ASICIb are expressed in the stereocilia of mouse cochlear hair cells. In-situ hybridization studies showed that ASICIb transcripts, but not ASICIa transcripts, were expressed in the inner and outer hair cells. Fluorescent immunohistochemical and immunogold electron microscopic analyses revealed that the ASICIb channels were located at the insertions of the stereocilia into the hair cells. Our findings provide a novel molecular key to the understanding of cochlear physiology and pathophysiology.