Efferent neurotransmitters in the human cochlea and vestibule

Acta Otolaryngol. 2007 Jan;127(1):13-9. doi: 10.1080/00016480600652123.


Conclusion: 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.

Materials and 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Calcitonin Gene-Related Peptide / immunology
  • Calcitonin Gene-Related Peptide / metabolism*
  • Choline O-Acetyltransferase / immunology
  • Choline O-Acetyltransferase / metabolism
  • Cochlea / enzymology
  • Cochlea / immunology
  • Cochlea / metabolism*
  • Ear, Inner / immunology
  • Ear, Inner / metabolism
  • Efferent Pathways / enzymology
  • Efferent Pathways / immunology*
  • Efferent Pathways / metabolism*
  • Enkephalins / immunology
  • Enkephalins / metabolism*
  • Humans
  • Immunohistochemistry
  • Neurotransmitter Agents / immunology*
  • Neurotransmitter Agents / metabolism*
  • Peptide Fragments / immunology
  • Peptide Fragments / metabolism*
  • Peripheral Nerves / immunology
  • Peripheral Nerves / metabolism
  • Temporal Bone / metabolism
  • Temporal Bone / pathology
  • Vestibule, Labyrinth / enzymology
  • Vestibule, Labyrinth / immunology
  • Vestibule, Labyrinth / metabolism*
  • gamma-Aminobutyric Acid / immunology
  • gamma-Aminobutyric Acid / metabolism*


  • Enkephalins
  • Neurotransmitter Agents
  • Peptide Fragments
  • calcitonin gene related peptide (1-7)
  • gamma-Aminobutyric Acid
  • Choline O-Acetyltransferase
  • Calcitonin Gene-Related Peptide