This is a proposal to identify and study the mechanism of cholinergic inhibition of cochlear hair cells using physiological, pharmacological, and molecular genetic analyses. We will also begin to examine the developmental regulation of this response. Efferent axons arising from cells in the brainstem provide an inhibitory input to outer hair cells in the mammalian and avian cochleas. This inhibitory effect is thought to result from the release of acetylcholine (ACh) from the efferent endings. Several lines of evidence point to the fact that the cholinergic response of cochlear hair cells may be mediated by a functionally unique ACh receptor (AChR). We propose to study the cholinergic response of hair cells isolated from the cochlea of the chick in an effort to understand the cellular and molecular bases of this inhibition. In addition, we intend to study the developmental acquisition of sensitivity to ACh in order to learn what factors govern the selective expression of these receptors in outer hair cells in adults. The experiments to meet these goals will be largely electrophysiological in nature, reflecting the established expertise of this laboratory. These will include whole-cell, cell-attached and excised patch voltage-clamp recordings. Also, we will use scanning confocal microscopy of intracellular signals from Ca-indicator dyes in order to assess the role of Ca as a second messenger in the hair cell response to ACh. The initial goal of our experiments in molecular biology will be to identify the genes coding for the hair cell AChR. We will first screen cochlear mRNA by RNAase protection using known brain alpha subunit clones. Another endeavor will be based on the polymerase chain reaction (PCR) to amplify cochlear cDNA that contains sequences coding for the bungarotoxin binding site in AChRs. In this way we may be able to identify a potentially unique cochlear AChR. The developmental acquisition of AChRs by hair cells will be studied during the last 10 days of embryogenesis, that is, preceding and spanning the time that efferent axons make synapses in the cochlea. Initially we will ask: when sensitivity to ACh arises, whether it is identical to mature responses, and whether all hair cells, or only presumptive outer hair cells, are sensitive? Later experiments will examine the effect of denervation and the role of activity in AChR acquisition. The motivation for this study is multi-part: to better understand the mechanism of cochlear inhibition, to contribute to the study of the molecular biology and biophysics of AChRs, and to begin to study the factors governing the developmental maturation of hair cell sensitivity to ACh.

Agency
National Institute of Health (NIH)
Institute
National Institute on Deafness and Other Communication Disorders (NIDCD)
Type
Research Project (R01)
Project #
1R01DC001508-01
Application #
3218126
Study Section
Hearing Research Study Section (HAR)
Project Start
1992-09-30
Project End
1995-08-31
Budget Start
1992-09-30
Budget End
1993-08-31
Support Year
1
Fiscal Year
1992
Total Cost
Indirect Cost
Name
University of Colorado Denver
Department
Type
Schools of Medicine
DUNS #
065391526
City
Aurora
State
CO
Country
United States
Zip Code
80045
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Boero, Luis E; Castagna, Valeria C; Di Guilmi, Mariano N et al. (2018) Enhancement of the Medial Olivocochlear System Prevents Hidden Hearing Loss. J Neurosci 38:7440-7451
Zachary, Stephen; Nowak, Nathaniel; Vyas, Pankhuri et al. (2018) Voltage-Gated Calcium Influx Modifies Cholinergic Inhibition of Inner Hair Cells in the Immature Rat Cochlea. J Neurosci 38:5677-5687
Moglie, Marcelo J; Fuchs, Paul A; Elgoyhen, Ana Belén et al. (2018) Compartmentalization of antagonistic Ca2+ signals in developing cochlear hair cells. Proc Natl Acad Sci U S A 115:E2095-E2104
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Wu, Ping-Feng; Chuang, Chien; Su, Chin-Fang et al. (2016) High minimum inhibitory concentration of imipenem as a predictor of fatal outcome in patients with carbapenem non-susceptible Klebsiella pneumoniae. Sci Rep 6:32665
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Rohmann, Kevin N; Wersinger, Eric; Braude, Jeremy P et al. (2015) Activation of BK and SK channels by efferent synapses on outer hair cells in high-frequency regions of the rodent cochlea. J Neurosci 35:1821-30
Goutman, Juan D; Elgoyhen, A Belén; Gómez-Casati, María Eugenia (2015) Cochlear hair cells: The sound-sensing machines. FEBS Lett 589:3354-61
Zachary, Stephen Paul; Fuchs, Paul Albert (2015) Re-Emergent Inhibition of Cochlear Inner Hair Cells in a Mouse Model of Hearing Loss. J Neurosci 35:9701-6

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