title: Ultrastructural localization of GABA-like immunoreactivity in the human utricular macula.
abstract: In the vertebrate vestibular periphery, gamma-aminobutyric acid (GABA) has long been presumed to be a neurotransmitter candidate. However, experimental reports about the localization and function of GABA in the vestibular systems of vertebrates are contradictory. In addition, there is no information in the literature concerning the localization of GABA in the human vestibular periphery. The present study investigates the ultrastructural localization of GABA-like immunoreactivity in the human utricular macula. A modified pre-embedding immunostaining electron microscopy technique was applied using two different commercially available polyclonal antibodies to GABA. GABA-like immunoreactivity is confined to the vesiculated nerve fibers and terminals of the human vestibular neurosensory epithelia. The GABA-containing nerve terminals make asymmetrical axo-dendritic synapses with the afferent chalices surrounding the type I sensory hair cells. Type I and type II hair cells as well as afferent chalices are devoid of GABA-like immunoreactive staining. The present study demonstrates that GABA exists in the human vestibular periphery, and that GABA is a neurotransmitter candidate of the human efferent vestibular system.
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; D004847:Epithelial Cells / Q000378:metabolism / Q000648:ultrastructure; D006801:Humans; D007150:Immunohistochemistry; D016253:Microscopy, Immunoelectron; D009412:Nerve Fibers / Q000378:metabolism* / Q000648:ultrastructure; D009475:Neurons, Afferent / Q000378:metabolism* / Q000648:ultrastructure; D013701:Temporal Bone / Q000294:innervation / Q000648:ultrastructure; D005680:gamma-Aminobutyric Acid / Q000032:analysis / Q000378:metabolism*
chemical_list: D005680:gamma-Aminobutyric Acid