SPATIAL AND TEMPORAL EXPRESSION PATTERNS OF NICOTINIC ACETYLCHOLINE ALPHA 9 AND ALPHA 10 SUBUNITS IN THE EMBRYONIC AND EARLY POSTNATAL INNER EAR

The expression and function of nicotinic receptor subunits (nAChRs) in the inner ear before the onset of hearing is not well understood. We investigated the mRNA expression of the alpha 9 and alpha 10 nAChR subunits in sensory hair cells of the embryonic and postnatal rat inner ear. We mapped their spatial and temporal expression in cochlear and vestibular hair cells using qPCR, [35S] labeled cRNA in situ hybridization, and alpha-bungarotoxin (alpha-Bgt) to label the presumptive membrane-bound receptor on cochlear hair cells. The results suggest that (1) the mRNA expression of the alpha 9 subunit precedes expression of the alpha 10 subunit in both cochlear and vestibular hair cells, (2) the mRNA expression of both the alpha 9 and alpha 10 subunits occurs earlier in the vestibular system than in the cochlea, (3) the mRNA expression of both subunits is required for the assembled receptor complexes, and (4) the presumptive assembled receptor, at least in the cochlea, is associated with synapse formation and the onset of function. (C) 2011 IBRO. Published by Elsevier Ltd. All rights reserved.