Naturally occurring mutant @entity19 provide an excellent model for the study of genetic @entity600 of the inner ear. @entity19 homozygous for the Bronx waltzer (bv/bv) mutation are severely hearing impaired or deaf and exhibit a 'waltzing' gait. Functional aspects of cochlear and vestibular efferents in the bv/bv mutant @entity19 are not well known. The present study was designed to evaluate several candidates of efferent neurotransmitters or neuromodulators including @entity1877 acetyltransferase ( @entity4268 ), @entity1246 ( @entity1246 ), and calcitonin gene-related peptide (CGRP) in the inner ear of the bv/bv mutant @entity19 . Ultrastructural investigations at both light and electron microscopic level were performed. Ultrastructural morphologic evaluations of the cochlea and the vestibular end-organs were also undertaken. It is demonstrated that @entity4268 , @entity1246 and CGRP immunoreactivities are present in the cochlea and in vestibular end-organs of bv/bv mutant @entity19 . In the organ of Corti, immunoreactivity of @entity4268 , @entity1246 and CGRP is confined to the inner spiral fibers, tunnel-crossing fibers, and the vesiculated nerve endings synapsing with outer hair cells. Interestingly, immunoreactivity was detectable even where inner hair cells appeared missing. Results also revealed @entity600 of the outer hair cells with synaptic contacts to efferent nerve endings consistently intact. In the neurosensory epithelia of the vestibular end-organs, the presence of @entity4268 , @entity1246 , and CGRP immunoreactivity was localized at the vestibular efferents, with the exception of the macula of saccule. In one 8-month-old macula of utricle where the depletion of hair cells appeared highest, @entity4268 immunostaining was still discernible. Ultrastructural investigation demonstrated that vesiculated efferent nerve endings make synaptic contact with the outer hair cells in the organ of Corti and with type II hair cells in the vestibular end-organs. The present study provides further support that the efferent system in the bv/bv mutant inner ear is morphologically as well as functionally mature. These findings also demonstrate that if and when the onset of efferent degeneration in the bv/bv mutant inner ear occurs, it transpires subsequent to pathological conditions in the hair cells. The present findings give further indication that the efferent systems of the bv/bv mutant inner ear are independent of the afferent systems in many aspects including development, maturation as well as degeneration.

Localization of efferent neurotransmitters in the inner ear of the homozygous Bronx waltzer mutant XXXX .

@entity1246 :: ('MESH:D005680', 'Chemical') :: ['gamma-aminobutyric acid', 'GABA'] @entity19 :: ('10090', 'Species') :: ['mice', 'mouse', 'Mice'] @entity4268 :: ('8063', 'Species') :: ['ChAT'] @entity600 :: ('MESH:D000014', 'Disease') :: ['malformations'] @entity1877 :: ('MESH:D002794', 'Chemical') :: ['choline']
@entity19 :: (10090,Species) :: ['mouse']
