Efferent neurotransmitters in the human cochlea and vestibule.
CONCLUSIONS
Current neurotransmission models based on animal studies on the mammalian inner ear not always reflect the situation in human. Rodents and primates show significant differences in characteristics of efferent innervation as well as the distribution of neuroactive substances.


OBJECTIVE
Immunohistochemistry demonstrates the mammalian efferent system as neurochemically complex and diverse: several neuroactive substances may co-exist within the same efferent terminal. Using light and electron microscopic immunohistochemistry, this study presents a comparative overview of the distribution patterns of choline acetyltransferase (ChAT), the acetylcholine synthesizing enzyme, GABA, CGRP, and enkephalins within the peripheral nerve fiber systems of the human inner ear.


METHODS
Human temporal bones were obtained post mortem and prepared according to a pre-embedding immunohistochemical technique to detect immunoreactivities to ChAT, GABA, CGRP, leu- and met-enkephalins at the electron microscopic level.


RESULTS
Immunoreactivities of all the antigens were present within both the lateral and medial efferent systems of the cochlea, whereas only ChAT, GABA, and CGRP were detected in efferent pathways of the vestibular end organs.
Schrott-Fischer
A
A
Department of Otolaryngology, Medical University of Innsbruck, Innsbruck, Austria.
Kammen-Jolly
K
K
Scholtz
A
A
Rask-Andersen
H
H
Glueckert
R
R
Eybalin
M
M
D015740:Calcitonin Gene-Related Peptide / Q000276:immunology / Q000378:metabolism*; D002795:Choline O-Acetyltransferase / Q000276:immunology / Q000378:metabolism; D003051:Cochlea / Q000201:enzymology / Q000276:immunology / Q000378:metabolism*; D007758:Ear, Inner / Q000276:immunology / Q000378:metabolism; D004525:Efferent Pathways / Q000201:enzymology / Q000276:immunology* / Q000378:metabolism*; D004745:Enkephalins / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D018377:Neurotransmitter Agents / Q000276:immunology* / Q000378:metabolism*; D010446:Peptide Fragments / Q000276:immunology / Q000378:metabolism*; D010525:Peripheral Nerves / Q000276:immunology / Q000378:metabolism; D013701:Temporal Bone / Q000378:metabolism / Q000473:pathology; D014722:Vestibule, Labyrinth / Q000201:enzymology / Q000276:immunology / Q000378:metabolism*; D005680:gamma-Aminobutyric Acid / Q000276:immunology / Q000378:metabolism*
D004745:Enkephalins; D018377:Neurotransmitter Agents; D010446:Peptide Fragments; C118482:calcitonin gene related peptide (1-7); D005680:gamma-Aminobutyric Acid; D002795:Choline O-Acetyltransferase; D015740:Calcitonin Gene-Related Peptide