ALPHA-9 - AN ACETYLCHOLINE-RECEPTOR WITH NOVEL PHARMACOLOGICAL PROPERTIES EXPRESSED IN RAT COCHLEAR HAIR-CELLS

We report the isolation and funational characterization of a member of the nicotinic acetylcholine receptor subunit gene family, alpha 9. Xe nopus oocytes injected with alpha 9 cRNA express a homomeric receptor- channel complex that is activated by acetylcholine. The alpha 9 recept or displays an unusual mixed nicotinic-muscarinic pharmacological prof ile. The unique properties of the alpha 9 receptor-channel complex clo sely match those described for the cholinergic receptor present in ver tebrate cochlear hair cells. In situ hybridization studies reveal a re stricted pattern of alpha 9 gene expression that includes the outer ha ir cells of the rat cochlea. Our results suggest that the alpha 9 rece ptor is involved in the cholinergic efferent innervation of cochlear h air cells and thus may modulate the encoding of auditory stimuli.