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Auditory Nuclei (auditory + nucleus)
Selected AbstractsDevelopmental changes in cell proliferation in the auditory midbrain of the bullfrog, Rana catesbeianaDEVELOPMENTAL NEUROBIOLOGY, Issue 11 2006Andrea Megela Simmons Abstract We examined patterns of cell proliferation in the auditory midbrain (torus semicircularis) of the bullfrog, Rana catesbeiana, over larval and early postmetamorphic development, by visualizing incorporation of 5-bromo-2,-deoxyuridine (BrdU) in cycling cells. At all developmental stages, BrdU-labeled cells were concentrated around the optic ventricle. BrdU-labeled cells also appeared within the torus semicircularis itself, in a stage-specific manner. The mitotic index, quantified as the percent of BrdU-positive cells outside the ventricular zone per total cells available for label, varied over larval development. Mitotic index was low in hatchling, early larval, and late larval stages, and increased significantly in deaf period, metamorphic climax, and froglet stages. Cell proliferation was higher in metamorphic climax than at other stages, suggesting increased cell proliferation in preparation for the transition from an aquatic to an amphibious existence. The change in mitotic index over development did not parallel the change in the total numbers of cells available for label. BrdU incorporation was additionally quantified by dot-blot assay, showing that BrdU is available for label up to 72 h postinjection. The pattern of change in cell proliferation in the torus semicircularis differs from that in the auditory medulla (dorsal medullary nucleus and superior olivary nucleus), suggesting that cell proliferation in these distinct auditory nuclei is mediated by different underlying mechanisms. © 2006 Wiley Periodicals, Inc. J Neurobiol 66: 1212,1224, 2006 [source] Cell proliferation in the Rana catesbeiana auditory medulla over metamorphic developmentDEVELOPMENTAL NEUROBIOLOGY, Issue 2 2006Judith A. Chapman Abstract During metamorphic development, bullfrogs (Rana catesbeiana) undergo substantial morphological, anatomical, and physiological changes as the animals prepare for the transition from a fully-aquatic to a semi-terrestrial existence. Using BrdU incorporation and immunohistochemistry, we quantify changes in cell proliferation in two key auditory brainstem nuclei, the dorsolateral nucleus and the superior olivary nucleus, over the course of larval and early postmetamorphic development. From hatchling through early larval stages, numbers of proliferating cells increase in both nuclei, paralleling the overall increase in total numbers of cells available for labeling. Numbers of proliferating cells in the superior olivary nucleus decrease during the late larval and deaf periods, and significantly increase during metamorphic climax. Proliferating cells in the dorsolateral nucleus increase in number from hatchling to late larval stages, decrease during the deaf period, and increase during climax. In both nuclei, numbers of proliferating cells decrease during the postmetamorphic froglet stage, despite increases in the number of cells available for label. Newly generated cells express either glial- or neural-specific phenotypes beginning between 1 week and 1 month post-BrdU injection, respectively, while some new cells express ,-aminobutyric acid within 2 days of mitosis. Our data show that these auditory nuclei dramatically up-regulate mitosis immediately prior to establishment of a transduction system based on atmospheric hearing. © 2005 Wiley Periodicals, Inc. J Neurobiol, 2005 [source] Morphologic and Neurochemical Abnormalities in the Auditory Brainstem of the Genetically Epilepsy-prone Hamster (GPG/Vall)EPILEPSIA, Issue 7 2005Verónica 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] Development of glutamate receptors in auditory neurons from long-term organotypic cultures of the embryonic chick hindbrainEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2009Carmen Diaz Abstract We used long-range organotypic cultures of auditory nuclei in the chick hindbrain to test the development of glutamate receptor activity in auditory neurons growing in a tissue environment that includes early deprivation of peripheral glutamatergic input, subsequent to removal of the otocyst. Cultures started at embryonic day (E)5, and lasted from 6 h to 15 days. Neuronal migration, clustering and axonal extension from the nucleus magnocellularis (NM) to the nucleus laminaris (NL) partially resembled events in vivo. However, the distinctive laminar organization of the NL was not observed. Glutamate receptor (GluR) activity was tested with optical recordings of intracellular Ca2+ in the NM. ,-Amino-3-hydroxy-5-methyl-4-isoxazoleproprionic acid (AMPA)/kainate receptors had Ca2+ responses with a time course similar to that in control slices. Peak amplitude, however, was significantly lower. N -methyl- d -aspartate (NMDA)-mediated Ca2+ responses were higher in 2-day cultures (E5 + 2d) than in E7 explant controls, returning later to control values. Metabotropic GluRs did not elicit Ca2+ responses at standard agonist doses. Blocking NMDA or AMPA/kainate receptors with specific antagonists for 10 days in culture did not limit neuronal survival. Blocking metabotropic GluRs resulted in complete neuronal loss. Thus, ionotropic GluRs are not required for NM neuronal survival. However, their activity during development is affected when neurons grow in an in vitro environment that includes prevention of arrival of peripheral glutamatergic input. [source] Calcium-binding protein immunoreactivity characterizes the auditory system of Gekko geckoTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 17 2010Kai Yan Abstract Geckos use vocalizations for intraspecific communication, but little is known about the organization of their central auditory system. We therefore used antibodies against the calcium-binding proteins calretinin (CR), parvalbumin (PV), and calbindin-D28k (CB) to characterize the gecko auditory system. We also examined expression of both glutamic acid decarboxlase (GAD) and synaptic vesicle protein (SV2). Western blots showed that these antibodies are specific to gecko brain. All three calcium-binding proteins were expressed in the auditory nerve, and CR immunoreactivity labeled the first-order nuclei and delineated the terminal fields associated with the ascending projections from the first-order auditory nuclei. PV expression characterized the superior olivary nuclei, whereas GAD immunoreactivity characterized many neurons in the nucleus of the lateral lemniscus and some neurons in the torus semicircularis. In the auditory midbrain, the distribution of CR, PV, and CB characterized divisions within the central nucleus of the torus semicircularis. All three calcium-binding proteins were expressed in nucleus medialis of the thalamus. These expression patterns are similar to those described for other vertebrates. J. Comp. Neurol. 518:3409,3426, 2010. © 2010 Wiley-Liss, Inc. [source] | ||||||||||