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Auditory Brainstem (auditory + brainstem)

Distribution by Scientific Domains

Life Sciences	71%

Terms modified by Auditory Brainstem

auditory brainstem response

Selected Abstracts

Morphologic and Neurochemical Abnormalities in the Auditory Brainstem of the Genetically Epilepsy-prone Hamster (GPG/Vall)

EPILEPSIA, Issue 7 2005
Verónica Fuentes-Santamaría
Summary:,Purpose: This study was performed to evaluate whether audiogenic seizures, in a strain of genetically epilepsy-prone hamsters (GPG/Vall), might be associated with morphologic alterations in the cochlea and auditory brainstem. In addition, we used parvalbumin as a marker of neurons with high levels of activity to examine changes within neurons. Methods: Cochlear histology as well as parvalbumin immunohistochemistry were performed to assess possible abnormalities in the GPG/Vall hamster. Densitometry also was used to quantify levels of parvalbumin immunostaining within neurons and fibers in auditory nuclei. Results: In the present study, missing outer hair cells and spiral ganglion cells were observed in the GPG/Vall hamster. In addition, an increase was noted in the size of spiral ganglion cells as well as a decrease in the volume and cell size of the cochlear nucleus (CN), the superior olivary complex nuclei (SOC), and the nuclei of the lateral lemniscus (LL) and the inferior colliculus (IC). These alterations were accompanied by an increase in levels of parvalbumin immunostaining within CN, SOC, and LL neurons, as well as within parvalbumin-immunostained fibers in the CN and IC. Conclusions: These data are consistent with a cascade of atrophic changes starting in the cochlea and extending along the auditory brainstem in an animal model of inherited epilepsy. Our data also show an upregulation in parvalbumin immunostaining in the neuropil of the IC that may reflect a protective mechanism to prevent cell death in the afferent sources to this nucleus. [source]

Tonotopic gradients of Eph family proteins in the chick nucleus laminaris during synaptogenesis

DEVELOPMENTAL NEUROBIOLOGY, Issue 1 2004
Abigail L. Person
Abstract Topographically precise projections are established early in neural development. One such topographically organized network is the auditory brainstem. In the chick, the auditory nerve transmits auditory information from the cochlea to nucleus magnocellularis (NM). NM in turn innervates nucleus laminaris (NL) bilaterally. These projections preserve the tonotopy established at the level of the cochlea. We have begun to examine the expression of Eph family proteins during the formation of these connections. Optical density measurements were used to describe gradients of Eph proteins along the tonotopic axis of NL in the neuropil, the somata, and the NM axons innervating NL at embryonic day 10, when synaptic connections from NM to NL are established. At E10,11, NL dorsal neuropil expresses EphA4 at a higher concentration in regions encoding high frequency sounds, decreasing in concentration monotonically toward the low frequency (caudolateral) end. In the somata, both EphA4 and ephrin-B2 are concentrated at the high frequency end of the nucleus. These tonotopic gradients disappear between E13 and E15, and expression of these molecules is completely downregulated by hatching. The E10,11 patterns run counter to an apparent gradient in dendrite density, as indicated by microtubule associated protein 2 (MAP2) immunolabeling. Finally, ephrin-B2 is also expressed in a gradient in tissue ventral to the NL neuropil. Our findings thus suggest a possible conserved mechanism for establishing topographic projections in diverse sensory systems. These results of this study provide a basis for the functional examination of the role of Eph proteins in the formation of tonotopic maps in the brainstem. © 2004 Wiley Periodicals, Inc. J Neurobiol 60: 28,39, 2004 [source]

Localization of KCNC1 (Kv3.1) potassium channel subunits in the avian auditory nucleus magnocellularis and nucleus laminaris during development

DEVELOPMENTAL NEUROBIOLOGY, Issue 2 2003
Suchitra Parameshwaran-Iyer
Abstract The KCNC1 (previously Kv3.1) potassium channel, a delayed rectifier with a high threshold of activation, is highly expressed in the time coding nuclei of the adult chicken and barn owl auditory brainstem. The proposed role of KCNC1 currents in auditory neurons is to reduce the width of the action potential and enable neurons to transmit high frequency temporal information with little jitter. Because developmental changes in potassium currents are critical for the maturation of the shape of the action potential, we used immunohistochemical methods to examine the developmental expression of KCNC1 subunits in the avian auditory brainstem. The KCNC1 gene gives rise to two splice variants, a longer KCNC1b and a shorter KCNC1a that differ at the carboxy termini. Two antibodies were used: an antibody to the N-terminus that does not distinguish between KCNC1a and b isoforms, denoted as panKCNC1, and another antibody that specifically recognizes the C terminus of KCNC1b. A comparison of the staining patterns observed with the panKCNC1 and the KCNC1b specific antibodies suggests that KCNC1a and KCNC1b splice variants are differentially regulated during development. Although panKCNC1 immunoreactivity is observed from the earliest time examined in the chicken (E10), a subcellular redistribution of the immunoproduct was apparent over the course of development. KCNC1b specific staining has a late onset with immunostaining first appearing in the regions that map high frequencies in nucleus magnocellularis (NM) and nucleus laminaris (NL). The expression of KCNC1b protein begins around E14 in the chicken and after E21 in the barn owl, relatively late during ontogeny and at the time that synaptic connections mature morphologically and functionally. © 2003 Wiley Periodicals, Inc. J Neurobiol 55: 165,178, 2003 [source]

Morphologic and Neurochemical Abnormalities in the Auditory Brainstem of the Genetically Epilepsy-prone Hamster (GPG/Vall)

Cysteine-string protein in inner hair cells of the organ of Corti: synaptic expression and upregulation at the onset of hearing

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 9 2002
Michel Eybalin
Abstract Cysteine-string protein is a vesicle-associated protein that plays a vital function in neurotransmitter release. We have studied its expression and regulation during cochlear maturation. Both the mRNA and the protein were found in primary auditory neurons and the sensory inner hair cells. More importantly, cysteine-string protein was localized on synaptic vesicles associated with the synaptic ribbon in inner hair cells and with presynaptic differentiations in lateral and medial olivocochlear terminals , the cell bodies of which lie in the auditory brainstem. No cysteine-string protein was expressed by the sensory outer hair cells suggesting that the distinct functions of the two cochlear hair cell types imply different mechanisms of neurotransmitter release. In developmental studies in the rat, we observed that cysteine-string protein was present beneath the inner hair cells at birth and beneath outer hair cells by postnatal day 2 only. We found no expression in the inner hair cells before about postnatal day 12, which corresponds to the period during which the first cochlear action potentials could be recorded. In conclusion, the close association of cysteine-string protein with synaptic vesicles tethered to synaptic ribbons in inner hair cells and its synchronized expression with the appearance and maturation of the cochlear potentials strongly suggest that this protein plays a fundamental role in sound-evoked glutamate release by inner hair cells. This also suggests that this role may be common to ribbon synapses and conventional central nervous system synapses. [source]

Spatio-temporal distribution of cellular retinoid binding protein gene transcripts in the developing and the adult cochlea.

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2000
CRBPI-null mutant mice, Morphological, functional consequences in CRABP-
Abstract The expression patterns of the mouse cellular retinoid binding protein genes were investigated by in situ hybridization analysis in the inner ear from 10.5 days post coïtum (dpc) up to the adult stage. The cellular retinoic acid binding protein II (CRABPII) and cellular retinol binding protein I (CRBPI) were present in a widespread and abundant pattern in cochlear structures during embryogenesis. Expression of the cellular retinoic acid binding protein I (CRABPI) is restricted during development in Kölliker's organ whilst cellular retinol binding protein II (CRBPII) is only visible after birth with a ubiquitous distribution in most regions of the cochlea including nervous components. No CRABP or CRBP transcripts were observed in the auditory receptors. Morphological observations of CRBPI- and CRABPI/CRABPII-null mutant fetus at 18.5 dpc do not show any structural modification at the level of the organ of Corti. Furthermore, electrophysiological tests performed by measuring distorsion-product otoacoustic emissions and auditory brainstem evoked responses did not present significant alteration of the auditory function for the different types of mutants. The expression of retinoid binding proteins in cochlear structures during embryogenesis could suggest important roles for these proteins during ontogenesis and morphogenesis of the inner ear. Despite these observations, morphological and functional data from mutant mice did not present obvious modifications of the cochlear structures and auditory thresholds. It is therefore unlikely that CRABPs and CRBPI are directly involved in development of the cochlea and hair cell differentiation. [source]

Comparative gene expression analysis reveals a characteristic molecular profile of the superior olivary complex

THE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 4 2006
Hans Gerd Nothwang
Abstract The superior olivary complex (SOC) is a very conspicuous structure in the mammalian auditory brainstem. It represents the first binaural processing center and is important for sound localization in the azimuth and in feedback regulation of cochlear function. In order to define molecular determinants of the SOC, which are of potential functional relevance, we have performed a comprehensive analysis of its transcriptome by serial analysis of gene expression in adult rats. Here, we performed a detailed analysis of the SOC's gene expression profile compared to that of two other neural tissues, the striatum and the hippocampus, and with extraocular muscle tissue. This tested the hypothesis that SOC-specific or significantly upregulated transcripts provide candidates for the specific function of auditory neurons. Thirty-three genes were significantly upregulated in the SOC when compared to the two other neural tissues. Thirteen encoded proteins involved in neurotransmission, including action potential propagation, exocytosis, and myelination; five genes are important for the energy metabolism, and five transcripts are unknown or poorly characterized and have yet to be described in the nervous system. The comparison of functional gene classes indicates that the SOC has the highest energy demand of the three neural tissues, yet protein turnover is apparently not increased. This suggests a high energy demand for fueling auditory neurotransmission. Such a demand may have implications on auditory-specific tasks and relate to central auditory processing disorders. Ultimately, these data provide new avenues to foster investigations of auditory function and to advance molecular physiology in the central auditory system. Anat Rec Part A, 2006. © 2006 Wiley-Liss, Inc. [source]