DOCSLIB.ORG

Doctoral (Ph.D.) Thesis NEW OBSERVATIONS on THE

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Doctoral (Ph.D.) Thesis NEW OBSERVATIONS on THE Doctoral (Ph.D.) Thesis NEW OBSERVATIONS ON THE ANATOMY OF THE OLIVOCOCHLEAR SYSTEM AND AUDITORY PATHWAY Dr. Miklós Horváth Tutors: Prof. Dr. Miklós Palkovits and Prof. Dr. Ottó Ribári Ph.D. School of the Semmelweis University Ph.D. School of Molecular Medicine (7) Program in Pathobiochemistry (7/2) Head of the Program: Prof. Dr. József Mandl Budapest, 2003 1. Introduction On the lowest level of the descending auditory system, a massive projection originates in the superior olivary complex of the brainstem to innervate outer and inner hair cells, or their immediate afferent synapses, in the cochlea. This olivocochlear system shares its developmental origin with facial branchial motor neurons and may be considered to be of the special visceral efferent type. The olivocochlear system was earlier considered to consists of two main populations of cells in the superior olivary complex. The medial olivocochlear cells (MOCs) reside in the ventral nucleus of the trapezoid body of both sides of the brain and innervate outer hair cells in the cochlea. Lateral olivocochlear cells (LOCs) are associated to the lateral nucleus of the superior olive (LSO), innervate predominantly the ipsilateral cochlea and terminate beneath the inner hair cells. The lateral olivocochlear neurons can be further divided into two subgroups. Small and fusiform cells are located within the ipsilateral LSO are termed intrinsic lateral olivocochlear neurons, while larger olivocochlear neurons are found in the periolivary regions around the lateral nucleus of the superior olive of both sides extending dendrites into the LSO and may be called shell neurons or shell LOCs. The collateral projections of olivocochlear cells were extensively studied in gerbil, mouse and guinea pig, but several controversies still exist about their pattern. Ryan reported that the unmyelinated intrinsic LOCs innervate mainly the central, and the myelinated MOCs the peripheral part of the ventral cochlear nucleus in gerbil. By contrast others found no cochlear nucleus collaterals of LOCs in gerbil, mouse and cat, but a majority of MOC axons was found to give off collaterals to granule cell containing regions of the ventral cochlear nucleus. White and Warr showed, by injecting horseradish peroxidase into the cochlea, that axons of olivocochlear cells leave the olivocochlear bundle at several points and enter the dorsal and ventral cochlear nuclei in rat. Position and number of cell bodies that belong to these collaterals have not been evaluated in detail. The nuclei of the ascending and descending auditory pathways are interconnected through a series of commissural and ipsilateral connections. Each stage of the descending auditory pathway could serve as descending part of regional feedback loops. In contrast to this “loop hypothesis”, some studies have indicated that descending auditory fibers form a continuous chain of neurons extending from the auditory cortex to the organ of Corti. To gain more insight into the nature of the descending auditory system several studies have investigated the possible sources of neuronal inputs to olivocochlear cells. The combination of retrograde and anterograde tracers could show some specific synaptic inputs to the olivocochlear cells. 2 Physiological and anatomical data indicate direct cortical innervation of olivocochlear cells. Descending projections from the inferior colliculus were also shown to terminate on olivocochlear neurons. Lateral olivocochlear neurons are innervated by cells of the ipsilateral posteroventral cochlear nucleus, while medial olivocochlear neurons receive inputs from the posteroventral and anteroventral cochlear nucleus bilaterally. In addition to these auditory connections, considerable evidence suggests the existence of peptidergic, noradrenergic and serotonergic inputs to olivocochlear neurons. New transneuronal tracing techniques have been developed, based on the use of alpha- herpesviruses (herpes simplex virus type 1 and pseudorabies virus) and rabies virus. These methods make it possible to identify functional networks of connected neurons. Following injection into peripheral organs or directly into the central nervous system, the viruses serve as self-amplifying markers. Virus-infected neurons can be visualized by routine immunocytochemical techniques. While the nervous system matures, the nerve cells go through a series of stages, each of which is characterized by a specific group of active genes and the expression of a specific set of proteins. One marker for distinctive developmental stages is the growth associated protein GAP-43. The protein GAP-43 (also called B-50, F1, pp46, P-57, or neuromodulin) is a membrane-associated phosphoprotein enriched in elongating axons and growth cones and it undergoes fast axonal transport in regenerating neurons. GAP-43 induces filopodia in non- neuronal cells and may directly contribute to growth cone activity by regulating cell membrane structure. It is a major substrate of the protein kinase C family and was found to be correlated with long-term synaptic potentiation in the rat hippocampus. With the onset of process outgrowth, intense GAP-43 immunoreactivity appears along the whole length of axons. At the end of this period of intense axonal staining, there is a brief interval in which high levels of GAP-43 immunostaining are seen in the neuropil. This period of dense neuropil staining coincides with the formation of axonal end-arbors, the beginning of synaptogenesis, and the time at which synaptic organization can be modified by the impinging pattern of activity. Later in development, staining in neuropil declines sharply in most regions except for certain structures in the rostral neuraxis which may be sites of ongoing synaptic remodeling. Apart from its role in development, however, it was shown that synaptic remodeling in the adult animal again raises levels of GAP-43 expression. GAP-43 is also part of the molecular machinery underlying long term potentiation, a cellular process related to learning and memory. In the adult animal, re-emergence of GAP-43 has been seen, for instance, in axotomized sensory and motor neurons. 3 2. Aims 2. 1. First, we attempted to monitor auditory brainstem development in the rat by using GAP- 43 as a developmental marker. The aim of our work was to determine the expression of GAP- 43 in the superior olive and cochlear nucleus in the early postnatal period and in adult animals. 2. 2. Second, we attempted to learn in detail, what kinds of changes occur in GAP-43 expression of the auditory brainstem after lesions to the spiral ganglion. Using GAP-43 as a marker for synaptogenesis and plasticity, we wanted to determine the plastic changes in the superior olive and cochlear nucleus following the loss of their inputs from the auditory periphery. 2. 3. Third, experiments were done to determine the distribution and number of olivocochlear cells that give off collaterals into the ventral cochlear nucleus en route to the cochlea in rat. The retrograde axonal tracers Diamidino Yellow and Fast Blue were used to label cell bodies of individual olivocochlear neurons and visualize cells that project to the cochlear nucleus. 2. 4. Fourth, the aim of our work was the transneuronal labeling of the descending auditory system by injecting the pseudorabies virus directly into the cochlea. This method allowed us to identify the olivocochlear cells and the sources of their inputs from other auditory and non- auditory neurons. 3. Methods 3. 1. To examine the postnatal development of GAP-43 immunoreactivity in the cochlear nucleus and superior olive, 30 Wistar rats were reared with their mothers with food and water available ad lib. Young animals were anaesthetized with lethal doses of barbiturate and their brains were removed and placed in ice-cold fixative. Older rats were killed by an overdose of Nembutal (Abbott) and perfused transcardially with 1 l ice-cold fixative for 1 hour. Thirty micron frontal or sagittal sections, cut on a cryostat, were collected in phosphate buffer. Immunocytochemical detection of GAP-43 was achieved with an antibody from mouse and a biotinylated anti-mouse immunoglobulin G secondary antibody. Peroxidase labeling was 4 visualized by using diaminobenzidine and ammonium nickel sulfate. Control sections that were incubated by omitting the primary antibody never showed staining of specific cellular elements. Great care was taken to keep the parameters influencing the outcome of the staining constant throughout the whole experimental series. 3. 2. Twenty-nine Wistar rats of both sexes were used to analyze the changes in GAP-43 expression of the auditory brainstem, following the removal of the left cochlea. The animals were deeply anaesthetized, the bulla tympani was approached and opened. The bony wall of the cochlea was perforated with a spherical drill head and the interior of the cochlea, including the spiral ganglion, was cleared. After different survival times (2, 4, 7, 14, 28, 56 days), animals were reanaesthetized with lethal doses of Nembutal and perfused transcardially with 1 l ice-cold fixative. Brains were cut on a cryostat into 30 µm thick frontal sections. Subsequently, sections were exposed to an anti-GAP-43 antibody, which is specified as recognizing GAP-43 independent of its state of phosphorylation. After incubation times of 72 hours at 4°C, binding-sites of the anti-GAP-43 antibody were detected using the avidin- biotin-technique with diaminobenzidine and ammonium nickel sulfate to intensify the colour of the reaction
Load more

Recommended publications
  • Synaptics and the Auditory Nerve;.Pdf
    Salamanca Study Abroad Program: Neurobiology of Hearing Synaptics and the auditory nerve R. Keith Duncan University of Michigan [email protected] Review Resources Reviews: Safieddine et al., 2012, The auditory hair cell ribbon synapse: From assembly to function, Ann Rev Neurosci, 35:509-528 Kim et al., 2013, Single Ca2+ channels and exocytosis at sensory synapses, J Physiol, epub Note: this is an excellent review describing the differences between cochlear and retinal ribbon synapses. Rabbitt and Brownell, 2011 Efferent modulation of hair cell function, Curr Opinion Otolaryngol Head Neck Surg,19:376-381 Outline Exocytosis and synaptics Afferent physiology Efferent physiology Afferent cochlear innervation Type 1 afferents: • 95% of cochlear afferents • account for hearing • each innervates only 1 IHC • ~20 innervate one IHC Type 2 afferents: • less well-described • en passant innervation of OHCs; 4 Hair cells form ribbon synapses with afferent neurons 5 Distinct pools of vesicles • Electron tomography reconstruction shows 4 pools Ribbon docked vesicles (readily releasable pool, ~10) Tethered vesicles (releasable pool, ~200) Extrasynaptic docked vesicles Cytoplasmic vesicles (recruitable pool?) • These pools likely contribute to distinct kinetics of exocytosis as Lenzi & von Gersdorff, 2001 stimulus duration increases. Distinct phases of exocytosis Capacitance is a proxy for exocytosis. Vesicle fusion increases surface area which increases capacitance. (see supplemental slides) Exocytosis occurs in calcium nanodomains Hair cells The synaptic vesicle cycle NT uptake, translocation, docking Molecular Components of Ribbon Synapses Differ from Conventional Synapses Vesicle related: • Synaptotagmins are the Ca2+ sensors in most synapses. Mature hair cells lack SYT I and II but have IV, VI-IX (rare types).
    [Show full text]
  • NIH Public Access Author Manuscript Curr Opin Otolaryngol Head Neck Surg
    NIH Public Access Author Manuscript Curr Opin Otolaryngol Head Neck Surg. Author manuscript; available in PMC 2012 October 01. NIH-PA Author ManuscriptPublished NIH-PA Author Manuscript in final edited NIH-PA Author Manuscript form as: Curr Opin Otolaryngol Head Neck Surg. 2011 October ; 19(5): 376–381. doi:10.1097/MOO. 0b013e32834a5be1. EFFERENT MODULATION OF HAIR CELL FUNCTION RICHARD D. RABBITT1,2 and WILLIAM E. BROWNELL3 1Department of Bioengineering, University of Utah, Salt Lake City, UT, USA 2Marine Biological Laboratory, Woods Hole, MA, USA 3Department of Otolaryngology, Head and Neck Surgery, Baylor College of Medicine, Houston, TX, USA Abstract Purpose of review—This review covers papers published between 2010 and early 2011 that presented new findings on inner ear-efferents and their ability to modulate hair cell function. Recent findings—Studies published within the review period have increased our understanding of efferent mechanisms on hair cells in the cochlear and vestibular sensory epithelium and provide insights on efferent contributions to the plasticity of bilateral auditory processing. The central nervous system controls the sensitivity of hair cells to physiological stimuli by regulating the gain of hair cell electromechanical amplification and modulating the efficiency of hair cell-8th nerve transmission. A notable advance in the past year has been animal and human studies that have examined the contribution of the olivocochlear efferents to sound localization particularly in a noisy environment. Summary—Acoustic activation of olivocochlear fibers provides a clinical test for the integrity of the peripheral auditory system and has provided new understanding about the function and limitations of the cochlear amplifier.
    [Show full text]
  • Cholinergic Top-Down Influences on the Auditory Brainstem
    Neuroforum 2017; 23(1): A35–A44 Thomas Künzel* and Hermann Wagner Cholinergic top-down influences on the auditory brainstem DOI 10.1515/nf-2016-A107 Sensory pathways are often mistakenly seen as purely ascending streams of information, where a given neuron Abstract: Descending connections are present in many feeds information only “upwards” to stations of increas- sensory systems and support adaptive information pro- ing complexity in a higher hierarchical level. In a well- cessing. This allows the sensory brain to code a wider known example, time-coding neurons in the cochlear range of inputs. A well characterized descending system nucleus are contacted by giant synaptic terminals of the is the olivo-cochlear cholinergic innervation of the inner auditory nerve (Felmy and Künzel, 2014) and pass infor- ear, which mediates a reduction of the sensitivity of the mation about the timing of the perceived sound up along inner ear upon perception of intense sounds. Because this the auditory pathway into binaural nuclei with more com- inhibits the response to background noise, the olivo-coch- plex functions. These neurons are clearly dominated by lear system supports detection of transient sound events. information flow from hierarchically lower to higher sta- Olivo-cochlear neurons also innervate the cochlear nucle- tions, as the ascending synaptic connection from the au- us through axon collaterals. Here, acetylcholine increases ditory nerve onto the time-coding neuron is very powerful. the excitability of central neurons without reducing their Although it is well established that the auditory periphery temporal precision. Thus their target neurons in the supe- and the first stages of the auditory pathway indeed show rior olivary complex can more effectively process binau- activity dependent dynamics, these adaptive phenomena ral temporal cues.
    [Show full text]
  • Subcollicular Projections to the Auditory Thalamus and Collateral Projections to the Inferior Colliculus
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Frontiers - Publisher Connector ORIGINAL RESEARCH ARTICLE published: 18 July 2014 NEUROANATOMY doi: 10.3389/fnana.2014.00070 Subcollicular projections to the auditory thalamus and collateral projections to the inferior colliculus Brett R. Schofield 1*, Jeffrey G. Mellott 1 and Susan D. Motts 2 1 Auditory Neuroscience Group, Department of Anatomy and Neurobiology, Northeast Ohio Medical University, Rootstown, OH, USA 2 Department of Physical Therapy, Arkansas State University, Jonesboro, AR, USA Edited by: Experiments in several species have identified direct projections to the medial geniculate Paul J. May, University of nucleus (MG) from cells in subcollicular auditory nuclei. Moreover, many cochlear nucleus Mississippi Medical Center, USA cells that project to the MG send collateral projections to the inferior colliculus (IC) Reviewed by: (Schofield et al., 2014). We conducted three experiments to characterize projections to Ranjan Batra, University of Mississippi Medical Center, USA the MG from the superior olivary and the lateral lemniscal regions in guinea pigs. For Edward Lee Bartlett, Purdue experiment 1, we made large injections of retrograde tracer into the MG. Labeled cells University, USA were most numerous in the superior paraolivary nucleus, ventral nucleus of the trapezoid *Correspondence: body, lateral superior olivary nucleus, ventral nucleus of the lateral lemniscus, ventrolateral Brett R. Schofield, Department of tegmental nucleus, paralemniscal region and sagulum. Additional sources include other Anatomy and Neurobiology, Northeast Ohio Medical University, periolivary nuclei and the medial superior olivary nucleus. The projections are bilateral 4209 State Route 44, PO Box 95, with an ipsilateral dominance (66%).
    [Show full text]
  • Corticofugal Modulation of Peripheral Auditory Responses
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Frontiers - Publisher Connector MINI REVIEW published: 30 September 2015 doi: 10.3389/fnsys.2015.00134 Corticofugal modulation of peripheral auditory responses Gonzalo Terreros 1 and Paul H. Delano 1,2* 1 Programa de Fisiología y Biofísica, ICBM, Facultad de Medicina, Universidad de Chile, Santiago, Chile, 2 Departamento de Otorrinolaringología, Hospital Clínico de la Universidad de Chile, Santiago, Chile The auditory efferent system originates in the auditory cortex and projects to the medial geniculate body (MGB), inferior colliculus (IC), cochlear nucleus (CN) and superior olivary complex (SOC) reaching the cochlea through olivocochlear (OC) fibers. This unique neuronal network is organized in several afferent-efferent feedback loops including: the (i) colliculo-thalamic-cortico-collicular; (ii) cortico-(collicular)-OC; and (iii) cortico-(collicular)-CN pathways. Recent experiments demonstrate that blocking ongoing auditory-cortex activity with pharmacological and physical methods modulates the amplitude of cochlear potentials. In addition, auditory-cortex microstimulation independently modulates cochlear sensitivity and the strength of the OC reflex. In this mini-review, anatomical and physiological evidence supporting the presence of a functional efferent network from the auditory cortex to the cochlear receptor is presented. Special emphasis is given to the corticofugal effects on initial auditory processing, that is, on CN, auditory nerve and
    [Show full text]
  • Putative Neurotransmitters in the Rat Cochlea at Several Ages
    366 Brain Research, 460 (1988) 36(~ 368 Elsevier BRE 23100 Putative neurotransmitters in the rat cochlea at several ages Douglas W. Hoffman 1, Kitty Lea Jones-King 1 and Richard A. Altschuler 2 INeurochemistry Laboratory. Departments of Psychiatry and Pharmacology, Dartmouth Medical School, Hanover, NH ( U. S. A. ) and 2Kresge Hearing Research Institute, University of Michigan, Ann Arbor, MI (U.S.A.) (Accepted 31 May 1988) Key words: Cochlea; Aging; Presbycusis; Enkephalin; Dynorphin; Acetylcholine We have performed a longitudinal study of the content of the putative neurotransminer substances, enkephalin, dynorphin, and acetylcholine (ACh), in the cochlea of the Fischer 344 rat. It is the first study of transmitters in the rat cochlea over an extended time span. This study also provides biochemical verification of the presence of ACh in cochlear tissues. No change was seen in the cochlear content of these transmitter candidates up to 24 months of age. In the past several years it has become clear that olivocochlear efferent fibers innervating the coch- there are anatomically and chemically distinct effer- lea 1-7'9~12'16"18-2°'23. These include enkephalins, dyn- ent systems innervating the cochlea; the lateral sys- orphins and neo-endorphins. Opioid receptors as tem, which terminates on eight nerve dendrites un- well have been reported in the cochlea m'2°. Enke- der inner hair cells, and the medial, which directly in- phalin- and dynorphin-like immunoreactivities have nervates outer hair cells 14'30~31. The lateral efferents also been seen in the same cells in the superior oli- of species studied to date are known to contain enke- vary region 1,7, as have opioid peptide-like and cho- phalins, dynorphins, calcitonin gene-retated peptide line acetyltransferase-like immunoreactivity 1,3, and and acetylcholine (ACh), while in the medial system enkephalin-like immunoreactivity and acetylcholin- only ACh has so far been identified as a putative esterase activity 5.
    [Show full text]
  • Of the Superior Olivary Complex in the Mexican Free-Tailed Bat, Tadarida Brasiliensis Mexicana
    THE JOURNAL OF COMPARATIVE NEUROLOGY 343:630-646 (1994) Anatomy and Projection Patterns of the Superior Olivary Complex in the Mexican Free-Tailed Bat, Tadarida brasiliensis mexicana BENEDIKT GROTHE, HERMANN SCHWEIZER, GEORGE D. POLLAK, GERD SCHULLER, AND CHRISTINA ROSEMA” Zoologisches Institut der Universitat Miinchen, 80333 Munchen, Germany (B.G., H.S., G.S., C.R.); and Department of Zoology, The University of Texas at Austin, Austin, Texas 78712 (G.D.P.) ABSTRACT The superior olivary complex (SOC) is the first station in the ascending auditory pathway that receives binaural projections. Two of the principal nuclei, the lateral superior olive (LSO) and the medial superior olive (MSO), are major sources of ascending projections to the inferior colliculus. Whereas almost all mammals have an LSO, it has traditionally been thought that only animals that hear low frequencies have an MSO. Recent reports, however, suggest that the medial part of the SOC in bats is highly variable and that at least some bats have a well-developed MSO. Thus, the main goal of this study was to evaluate the cytoarchitectureand connections of the principal superior olivary nuclei of the Mexican free-tailed bat, with specific attention directed at the MSO. Cell and fiber stained material revealed that the LSO and the medial nucleus of the trapezoid body (MNTB) are similar to those described for other mammals. There are two medial nuclei we refer to as dorsomedial periolivary nucleus (DMPO) and MSO. Tracer experiments exhibited that the DMPO receives bilateral projections from the cochlear nucleus, and additional projections from the ipsilateral MNTB. The DMPO sends a strong projection to the ipsilateral inferior colliculus.
    [Show full text]
  • THESIS for DOCTORAL DEGREE (Ph.D.)
    From DEPARTMENT OF CLINICAL SCIENCE, INTERVENTION AND TECHNOLOGY Division of Audiology Karolinska Institutet, Stockholm, Sweden CELLULAR CORRELATES OF SENSORY PROCESSING IN THE MAMMALIAN AUDIO-VESTIBULAR BRAINSTEM Sara Leijon Stockholm 2016 All previously published papers were reproduced with permission from the publisher. Published by Karolinska Institutet. Printed by E-print, Solna, Stockholm © Sara Leijon, 2016 ISBN 978-91-7676-195-3 DEPARTMENT OF CLINICAL SCIENCE, INTERVENTION AND TECHNOLOGY, DIVISION OF AUDIOLOGY Cellular Correlates of Sensory Processing in the Mammalian Audio-Vestibular Brainstem THESIS FOR DOCTORAL DEGREE (Ph.D.) By Sara Leijon Principal Supervisor: Opponent: Associate Professor Anna K. Magnusson Professor Ian D. Forsythe Karolinska Institutet University of Leicester Division of Audiology Department of Neuroscience Department of CLINTEC Examination Board: Co-supervisor(s): Dr. Jens Hjerling-Leffler Dr. Neil Portwood Karolinska Institutet Karolinska Institutet Department of Medical Biochemistry and Department of Molecular Medicine and Surgery Biophysics Professor Anders Fridberger Professor Mary Rudner Linköping University Linköping University Department of Clinical and Experimental Medicine Department of Behavioural Sciences and Learning Professor Bryndis Birnir Uppsala University Department of Neuroscience Stockholm 2016 “Try to learn something about everything, and everything about something.” Thomas Huxley I am naturally curious and I love to learn. I love traveling to distant places I have never seen, experiencing new cultures, and communicating in new languages. I guess that’s my ‘something about everything’. I also have an inborn curiosity about the world and how it functions. I guess that is why science has become my ‘everything about something’. Photo: Ola Orvar Dedicated to my mother. For always encouraging me to stay curious; no matter where or how far that curiosity will lead me.
    [Show full text]
  • Olivocochlear Efferents
    Lauer et al. 2012 Olivocochlear efferents Amanda M. Lauer, Ph.D. Dept. of Otolaryngology-HNS May 30, 2016 Overview • Structural organization • Responses • Hypothesized roles in hearing Olivocochlear efferent pathways Brown and Levine, 2008 Lauer et al., 2012 Darrow et al., 2007 Terminal branching patterns Liberman and Brown 1986 Brown 2011 The terminal branching of the three types of olivocochlear efferents is different. MOC efferent reflex circuit + Darrow et al. 2012 Hypothesized lateral efferent circuit Darrow et al. 2007 MOC efferents show frequency specific responses to sound Liberman and Brown 1986 MOCs operate via the alpha9-alpha10 acetylcholine receptor to suppress OHCs Wersinger & Fuchs, 2011 Alpha9 KO Lauer and May, 2011 Vetter et al., 1999 Classic effects of olivocochlear bundle stimulation on auditory nerve responses MOC stimulation alters auditory nerve firing to extend dynamic range in quiet and reduce masking in noise From Guinan (2006) Ear and Hearing review; early work by Winslow & Sachs Hypothesized roles in hearing • Anti-masking/hearing in noise • Protection from noise • Selective attention • Sound localization & binaural balancing • Age-related hearing loss • Guiding development Anti-masking/Hearing in Noise Speech sound discrimination deficits in noise after OC lesions Cats trained to discriminate frequency changes in f2 of vowels in background noise Detected small changes prior to surgery Hienz et al. 1998 Required larger frequency differences to make the discrimination in noise after lesion; behavior in quiet is unchanged But…A9KO have normal hearing in noise Detect tone Detect change in tone in noise intensity in noise May et al., 2002 OCB lesions affect sound localization in noise Cats trained to discriminate change in location of sounds in median vertical plane Performance is disrupted in noise, but not quiet in bilaterally lesioned animals Suggests MOC activation normally unmasks spectral (pinna) cues Not shown: thresholds return to normal after a while May, B.
    [Show full text]
  • Preventing Presbycusis in Mice with Enhanced Medial Olivocochlear Feedback
    Preventing presbycusis in mice with enhanced medial olivocochlear feedback Luis E. Boeroa,b,1, Valeria C. Castagnaa,b,1, Gonzalo Terrerosc,d, Marcelo J. Moglieb, Sebastián Silvad,e,f, Juan C. Maassd,e,f, Paul A. Fuchsg, Paul H. Delanod,h, Ana Belén Elgoyhena,b, and María Eugenia Gómez-Casatia,2 aInstituto de Farmacología, Facultad de Medicina, Universidad de Buenos Aires, 1121 Buenos Aires, Argentina; bInstituto de Investigaciones en Ingeniería Genética y Biología Molecular, Dr. Héctor N. Torres, Consejo Nacional de Investigaciones Científicas y Técnicas, 1428 Buenos Aires, Argentina; cInstituto de Ciencias de la Salud, Universidad de O’Higgins, 2841935 Rancagua, Chile; dLaboratory of Auditory Neurobiology, Auditory and Cognition Center, 8380453 Santiago, Chile; ePrograma Interdisciplinario de Fisiología y Biofísica, Instituto de Ciencias Biomédicas, Universidad de Chile, 8380453 Santiago, Chile; fDepartamento de Otorrinolaringología, Facultad de Medicina, Universidad de Chile, 8380453 Santiago, Chile; gThe Center for Hearing and Balance, Otolaryngology-Head and Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, MD 21205; and hDepartamento de Neurociencia y Otorrinolaringología, Facultad de Medicina, Universidad de Chile, 8380453 Santiago, Chile Edited by Dan H. Sanes, New York University, New York, NY, and accepted by Editorial Board Member J. Anthony Movshon April 1, 2020 (received for review January 19, 2020) “Growing old” is the most common cause of hearing loss. Age- attributed to damage to peripheral sensory and neural elements, related hearing loss (ARHL) (presbycusis) first affects the ability as well as changes occurring along the central auditory pathway to understand speech in background noise, even when auditory (9–11). Peripheral degeneration involves the degeneration of the thresholds in quiet are normal.
    [Show full text]
  • Localization of Preproenkephalin Mrna-Expressing Cells in Rat Auditory Brainstem with in Situ Hybridization
    Hearing Research, 69 (1993) l-9 0 1993 Elsevier Science Publishers B.V. All rights reserved 037%595>/93/$06.00 HEARES 01953 Localization of preproenkephalin mRNA-expressing cells in rat auditory brainstem with in situ hybridization Douglas W. Hoffman ayb,Jill S. Hochreiter a, Douglas R. Landry apb,Megan R. Brimijoin a, Melinda D. Treadwell b, Paul D. Gardner ’ and Richard A. Altschuler d Departments of a Psychiatry, b Pharmacology, and ’ Biochemistry, Dartmouth Medical School, Hanover, New Hampshire and d Kresge Hearing Research Institute, University of Michigan, Ann Arbor, Michigan, USA (Received 25 August 1992; Revision received 29 March 1993; Accepted 2 April 1993) Hair cells and auditory nerve dendrites in the inner ear are innervated by pontine neurons that have been demonstrated by immunochemical techniques to contain several neurotransmitters, including acetylcholine and the opioid peptide enkephalins and dynorphins. The functions of these nerve fibers are not known, but may involve modifying auditory sensitivity to low intensity stimuli. In the guinea pig the opioid pathways originate in the lateral superior olivaIy region. A recent study in the gerbil has reported cells expressing preproenkephalin mRNA present only in the ventral nucleus of the trapezoid body, and not in the superior olivary region. In the present study, a non-radioisotopically labeled in situ hybridization method was used to identify cells expressing mRNA coding for preproenkephalin in rat pontine neurons, specifically in the ventral nucleus of the trapezoid body. These cells may represent an enkephalin-containing medial olivocochlear system in the rat, the origin of the lateral system in the rat that differs markedly from the better-studied guinea pig and cat, or a non-olivocochlear enkephalin-containing system.
    [Show full text]
  • Audiologic Findings in Unilateral Deafness from Contralateral Pontine
    Audiologic findings in unilateral deafness resulting from contralateral pontine infarct KAREN JO DOYLE, MD, PhD, CYNTHIAFOWLER, PhD, and ARNOLD STARR, MD, Irvine and Long Beach, California Focal brain stem infarction has been uncommonly from April 1994 demonstratd a dorsally located infarct associated with unilateral sensorineural hearing loss involving the medial left portion of the upper pons, as well (SNHL). Kumar et al. (1986) 1 found a single case of as ischemic changes of the periventricular deep white brain stem infarction among 200 cases of unilateral matter (Figs. 1 and 2). SNHL. Previous case reports of unilateral SNHL He was referred 3 weeks after the stroke to the Audi- ology Department for evaluation of his right-sided hearing after brain stem infarct have been the result of loss. Audiogram revealed a fiat, severe SNHL in the right lesions of the ipsilateral cochlear nuclei in the dor- ear and a moderate high-frequency SNHL above 2000 Hz solateral medulla. 2,3 Wada and Starr (1983) 4 deter- in the left ear (Fig. 3). Speech discrimination was 0% in mined that an experimentally produced lesion of the the right ear and 92% in the left ear. Acoustic reflexes lateral lemniscus produced a unilateral contralateral were absent in the right ear. ABR was performed with abnormality in the N 3 portion of wave III of the condensation and rarefaction dicks presented 10/second auditory brain stem response (ABR) in guinea pigs. at 95 dB nSL (Fig. 4). In the left ear, all components were We report a case of unilateral SNHL after a con- identified, and their intercomponent times were within tralateral focal pontine infarct verified by magnetic normal limits.
    [Show full text]