Selective retrograde labeling of lateral olivocochlear neurons in the brainstem based on preferential uptake of 3H-D-aspartic acid in the cochlea
We have previously shown that perfusion of the gerbil cochlea with probe concentrations of /sup 3/H-D-aspartic acid (D-ASP) results in immediate, selective labeling of 50-60% of the efferent terminals under the inner hair cells, presumably by high-affinity uptake. The present study was undertaken to determine the origin of these endings. Twenty-four hours after cochlear perfusion with D-ASP, labeled neurons were observed in the ipsilateral, and to a much lesser extent in the contralateral, lateral superior olivary nucleus (LSO). The cells were small, primarily fusiform, and showed fewer synaptic contacts than other LSO cells. Combined transport of D-ASP and horseradish peroxidase indicated that all olivocochlear neurons within the LSO that projected to the injected cochlea were labeled by D-ASP. Labeled fibers coursed dorsally from the LSO, joined contralateral fibers that had passed under the floor of the fourth ventricle, and entered the VIIIth nerve root at its ventromedial edge. Adjacent to the ventral cochlear nucleus (VCN), densely labeled collateral fibers crossed the nerve root to enter the VCN. Labeled fibers and terminals were prominent in the central VCN. Neither retrograde transport of D-ASP by medial olivocochlear and vestibular efferents nor anterograde transport by VIIIth nerve afferents was observed. The D-ASP-labeled cells and fibers are clearly lateral olivocochlear efferents. Retrograde transport of D-ASP thus allows the cells, axons, and collaterals of the lateral olivocochlear system to be studied, morphologically, in isolation from other cells that project to the cochlea. Since the olivocochlear neurons are almost certainly cholinergic, retrograde amino acid transport does not necessarily identify the primary neurotransmitter of a neuron. Rather, it indicates the presence of selective uptake by the processes of that neuron at the site of amino acid injection.
- Research Organization:
- Veterans Administration Medical Center, San Diego, CA
- OSTI ID:
- 6859360
- Journal Information:
- J. Comp. Neurol.; (United States), Vol. 4
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ASPARTIC ACID
MEMBRANE TRANSPORT
AUDITORY ORGANS
BIOLOGICAL FUNCTIONS
PHYSIOLOGY
BRAIN
CELL NUCLEI
GERBILS
LABELLING
NERVE CELLS
PERFUSED TISSUES
TRITIUM COMPOUNDS
AMINO ACIDS
ANIMAL CELLS
ANIMAL TISSUES
ANIMALS
BODY
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CENTRAL NERVOUS SYSTEM
FUNCTIONS
LABELLED COMPOUNDS
MAMMALS
NERVOUS SYSTEM
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANS
RODENTS
SENSE ORGANS
SOMATIC CELLS
TISSUES
VERTEBRATES
551001* - Physiological Systems- Tracer Techniques