A Study of Neurotransmitters in Human Inner Ear: Preservation of Human Temporal Bone and Value of Organ Donation for Inner Ear Research

Abstract

Twenty-nine human temporal bones (TBs) from 3 different groups of patients were used to investigate an effective preservation method of the inner ear and to study the suitability of TBs from organ donors for human inner ear research. Inner ears were fixed by perilymphatic perfusion and immersion fixation. Choline acetyltransferase (ChAT) and gamma-aminobutyric acid (GABA) activities were detected either by an indirect immunostaining method or by the peroxidase-antiperoxidase (PAP) technique. The results show that the cytoarchitecture of the sensory epithelia is excellently preserved in specimens fixed within 2 h after death. ChAT- and GABA-immunoreactivities were revealed in the efferent nerve endings and fibers of the cochlea. Morphological preservation of the sensory epithelia was also good in specimens fixed within 5 h after death. However, inner ear sensory epithelia of organ donors that had died from head trauma and were in the definite brain death state for at least 7¹/₂h were severely damaged and showed cellular debris due to autolysis, although they were fixed within 2¹/₂h after death. The mechanisms underlying this damage of the sensory epithelia are discussed.

Key Words:

• cochlea
• vestibule
• explantation
• immunocytochemistry
• neurotransmitters.