Brainstem branches from olivocochlear axons in cats and rodents

Brown, M. Christian; Liberman, M. Charles; Benson, Thane E.; Ryugo, David K.

doi:10.1002/cne.902780410

Cited by 162 publications

(103 citation statements)

References 41 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…As reported previously, the vesicles in the type II terminals were figure). In successive figures, the orientation is reversed (dorsal toward the bottom of the figure) in order to be consistent with our previous work (Brown et al 1988b;Benson and Brown 1990;Benson et al 1996).…”

Section: Synapses From Type II Swellingssupporting

confidence: 82%

“…Methods for our injections and processing appear in previous publications (Brown et al 1988b;Benson and Brown 1990). All experimental procedures on animals were in accordance with the National Institutes of Health guidelines for the care and use of laboratory animals and were performed under approved protocols at the Massachusetts Eye & Ear Infirmary.…”

Section: Methodsmentioning

confidence: 99%

“…The cochlear nucleus was blocked, embedded in a mixture of gelatin and albumin (0.5% and 27%, respectively) that was hardened by the addition of glutaraldehyde (2.3% of total volume), and sectioned (50 lm thickness) on a Vibratome in the sagittal plane. Free-floating sections were processed to reveal the HRP reaction product within the labeled fibers (Fekete et al 1984;Brown et al 1988b;Benson and Brown 1990) using diaminobenzidine as the chromogen and adding 1% dimethylsulfoxide to solutions containing cobalt or diaminobenzidine. After postfixation in 1% osmium tetroxide for 15 min, the sections were stained en bloc with saturated, filtered uranyl acetate (1 h), dehydrated with methanol, infiltrated with epoxy, and flatembedded between two transparent sheets of Aclar (Pro Plastics, Wall, NJ).…”

Section: Methodsmentioning

confidence: 99%

“…The lengths of apposition between labeled terminals and their targets, and the lengths of the associated postsynaptic densities, were measured in all sections containing the labeled synaptic terminal. We identified the few labeled branches of olivocochlear axons by their thick diameters, more frequent swellings, and orientation in a more mediolateral direction (Brown et al 1988b;Benson and Brown 1990), and with careful correlation of the light and serial electron microscopic images, we discriminated between labeled fiber types. Unlabeled target dendrites of synapses from type II fibers, as well as other unlabeled dendrites in the electron micrographs, were assigned individual identifiers and followed from section-to-section by alignment with relation to nearby fiducial marks that included other dendrites, axons, somata, and blood vessels.…”

Section: Methodsmentioning

confidence: 99%

“…Thus, for several reasons, the granule-cell lamina offers a promising site to examine type II swellings for their synapses and their postsynaptic targets. In addition to type II inputs, the lamina also receives a wide variety of auditory descending inputs from sources such as the superior olivary complex (Rasmussen 1960;Martin 1981;Osen et al 1984;Ryan et al 1987;Brown et al 1988b), inferior colliculus (Caicedo and Herbert 1993;Saldana 1993), and auditory cortex . Additional inputs arise from nonauditory sources (Itoh et al 1987;Weinberg and Rustioni 1987;Burian and Gstoettner 1988;Kevetter and Perachio 1989).…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Postsynaptic Targets of Type II Auditory Nerve Fibers in the Cochlear Nucleus.

Benson

Brown

2004

JARO

View full text Add to dashboard Cite

Type II auditory nerve fibers, which provide the primary afferent innervation of outer hair cells of the cochlea, project thin fibers centrally and form synapses in the cochlear nucleus. We investigated the postsynaptic targets of these synapses, which are unknown. Using serial-section electron microscopy of fibers labeled with horseradish peroxidase, we examined the border of the granule-cell lamina in mice, an area of type II termination that receives branches having swellings with complex shapes. About 70% of the swellings examined with the electron microscope formed morphological synapses, which is a much higher value than found in previous studies of type II swellings in other parts of the cochlear nucleus. The high percentage of synapses enabled a number of postsynaptic targets to be identified. Most of the targets were small dendrites. Two of these dendrites were traced to their somata of origin, which were cochlear-nucleus ''small cells'' situated at the border of the granule-cell lamina. These cells did not appear to receive any terminals containing synaptic vesicles that were large and round, indicating a lack of input from type I auditory nerve fibers. Nor did type II swellings or targets participate in the synaptic glomeruli formed by mossy terminals and the dendrites of granule cells. Other type II synapses were axosomatic and their targets were large cells, which were presumed multipolar cells and one cell with characteristics of a globular bushy cell. These large cells almost certainly receive additional input from type I auditory nerve fibers, which provide the afferent innervation of the cochlear inner hair cells. A few type II postsynaptic targets-the two small cells as well as a large dendrite-received synapses that had accompanying postsynaptic bodies, a likely marker for synapses of medial olivocochlear branches. These targets thus probably receive convergent input from type II fibers and medial olivocochlear branches. The diverse nature of the type II targets and the examples of segregated convergence of other inputs illustrates the synaptic complexity of type II input to the cochlear nucleus.

show abstract

Section: Synapses From Type II Swellingssupporting

confidence: 82%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Postsynaptic Targets of Type II Auditory Nerve Fibers in the Cochlear Nucleus.

Benson

Brown

2004

JARO

View full text Add to dashboard Cite

show abstract

Mossy fiber projections from the cuneate nucleus to the cochlear nucleus in the rat

1996

View full text Add to dashboard Cite

A reciprocal connection is known to exist between the cuneate nucleus, which is a first-order somatosensory nucleus, and the cochlear nucleus, which is a first-order auditory nucleus. We continued this line of study by investigating the fiber endings of this projection in the cochlear nucleus of rats using the neuronal tracer Phaseolus vulgaris leucoagglutinin in combination with ultrastructural and immunocytochemical analyses. In the cochlear nucleus, mossy fiber terminals had been described and named for their morphologic similarity to those in the cerebellum, but their origins had not been discovered. In the present study, we determined that the axonal projections from the cuneate region gave rise to mossy fiber terminals in the granule cell regions of the ipsilateral cochlear nucleus. The cuneate mossy fibers appear to be excitatory in nature, because they are filled with round synaptic vesicles, they make asymmetric synapses with postsynaptic targets, and they are labeled with an antibody to glutamate. The postsynaptic targets of the mossy fibers include dendrites of granule cells. This projection onto the granule cell interneuron circuit of the cochlear nucleus indicates that somatosensory cues are intimately involved with information processing at this early stage of the auditory system.

show abstract

Synaptic input to cochlear nucleus dendrites that receive medial olivocochlear synapses

1996

Self Cite

View full text Add to dashboard Cite

Axons of olivocochlear neurons originate in the superior olivary complex and project to the cochlea. Along their course, medial olivocochlear axons give off branches to the cochlear nucleus. We labeled these branches with horseradish peroxidase and used electron microscopy to determine their target dendrites. Target dendrites were of two classes: "large" dendrites and "varicose" dendrites. Using serial sections, we reconstructed the dendrites and, in addition to the labeled olivocochlear input, we determined the synaptic profile of unlabeled inputs onto the dendrites. We classified the terminals on the basis of the shape and size of their synaptic vesicles. On large dendrites, the predominant type of unlabeled terminal had small round (SmRnd) vesicles. These terminals are likely to be excitatory, and some of them may originate from unlabeled medial olivocochlear branches. On varicose dendrites, the predominant type of terminal had pleomorphic vesicles. These terminals are likely to be inhibitory. They may be from descending inputs that arise in higher centers. A final type of terminal onto large dendrites exhibited signs of neuronal degeneration, possibly because the cell body of origin was damaged during the injection procedure. These terminals often had long, perforated synaptic densities and may originate from type II primary afferents. Thus, medial olivocochlear efferents and type II afferents, which both contact outer hair cells in the periphery, appear to synapse onto the same targets in the cochlear nucleus. In contrast, where examined, the target dendrites did not receive terminals with large vesicles from afferents that contact inner hair cells. Thus, target neurons appear to function in a neural circuit associated more closely with outer than with inner hair cells.

show abstract

Brainstem branches from olivocochlear axons in cats and rodents

Cited by 162 publications

References 41 publications

Postsynaptic Targets of Type II Auditory Nerve Fibers in the Cochlear Nucleus.

Postsynaptic Targets of Type II Auditory Nerve Fibers in the Cochlear Nucleus.

Mossy fiber projections from the cuneate nucleus to the cochlear nucleus in the rat

Synaptic input to cochlear nucleus dendrites that receive medial olivocochlear synapses

Contact Info

Product

Resources

About