title: Ultrastructural localization of ChAT-like immunoreactivity in the human vestibular periphery.
abstract: Acetylcholine (ACh) has long been considered a neurotransmitter candidate in the efferent vestibular system of mammals. Recently, choline acetyltransferase (ChAT), the synthesizing enzyme for ACh, was immunocytochemically localized in all five end-organs of the rat vestibule (Kong et al. (1994) Hear. Res. 75, 192-200). However, there is little information in the literature concerning the cholinergic innervation in the vestibular periphery of man. In the present study the ultrastructural localization of the ChAT-like immunoreactivity in the human vestibular periphery was investigated in order to reveal the cholinergic innervation in the human vestibular end-organs. A modified method of pre-embedding immunoelectron microscopy was applied. It was found that the ChAT-like immunoreactivity was located in the bouton-type vesiculated nerve terminals in the vestibular neurosensory epithelia of man. These ChAT-like immunostained nerve terminals make synaptic contacts either with afferent chalices surrounding type I vestibular sensory hair cells, or with type II vestibular sensory hair cells. These results show that the ChAT-like immunoreactivity in the human vestibular periphery is confined to the efferent vestibular system. The ChAT-containing efferents innervate both type I hair cells and type II hair cells, making postsynaptic and presynaptic contacts, respectively. This study presents evidence that ACh is a neurotransmitter candidate in the efferent vestibular system of man.
authors.affiliation: Department of Otolaryngology, University Hospital of Innsbruck, Austria.
authors.forename: W J
authors.initials: WJ
authors.lastname: Kong
authors.forename: B
authors.initials: B
authors.lastname: Hussl
authors.forename: W F
authors.initials: WF
authors.lastname: Thumfart
authors.forename: A
authors.initials: A
authors.lastname: Schrott-Fischer
mesh_terms: D008267:Acoustic Maculae / Q000294:innervation* / Q000648:ultrastructure; D001344:Autopsy; D002795:Choline O-Acetyltransferase / Q000032:analysis / Q000378:metabolism*; D004847:Epithelial Cells / Q000201:enzymology / Q000648:ultrastructure; D006801:Humans; D007150:Immunohistochemistry; D016253:Microscopy, Immunoelectron; D009475:Neurons, Afferent / Q000201:enzymology / Q000648:ultrastructure; D009476:Neurons, Efferent / Q000201:enzymology / Q000648:ultrastructure; D010477:Perfusion; D010498:Perilymph; D013701:Temporal Bone / Q000294:innervation* / Q000648:ultrastructure
chemical_list: D002795:Choline O-Acetyltransferase