# Synaptic mechanisms in the auditory system

> **NIH NIH R01** · OREGON HEALTH & SCIENCE UNIVERSITY · 2020 · $63,812

## Abstract

Project Summary
Early stages of neural processing are informed by later stages, and this descending control plays multiple,
important roles. Among sensory systems, descending control in the auditory system is probably most complex,
and therefore least understood. The olivocochlear efferent system is a reflex pathway that modifies the
response of the organ of Corti to acoustic signals. Here we focus on the medial olivocochlear system (MOC),
which through a sophisticated cholinergic mechanism protects against acoustic damage and enhances the
ability of the cochlea to detect signals in noise. MOC cells receive glutamatergic reflex input from cochlear
nucleus but also descending input from cortex and midbrain. Moreover, MOC neurons excited by acetylcholine
receptor agonists suggesting local cholinergic influences. How these distinct inputs function relative to one
another is unknown. Indeed, the literature has not clarified functional differences in these inputs because of
limitations in the classical physiological or anatomical approaches to independently activate different neural
pathways to the MOC neurons. Here we propose to use modern mouse genetic and optogenetic techniques
combined with electrophysiology in a brain slice system to determine the intrinsic and synaptic properties that
underlie olivocochlear function. An additional point of control of MOC system is through MOC collaterals made
in the cochlear nucleus, which ultimately feeds back to MOC cells. How cholinergic signaling from MOC and
from midbrain pedunculopontine tegmental controls the MOC is unknown. A working hypothesis is that MOC
and PPT act on distinct microcircuits in cochlear nucleus and that this translates to differential feedback control
to MOC via the IC. This will be tested here using electrophysiological and optogenetic analysis of cholinergic
influences in the cochlear nucleus in vitro and in vivo. Because the MOC system plays an essential in
protection against noise damage, it is likely that the results of this study will lead to a better means to prevent
damage to, or recover, human hearing.

## Key facts

- **NIH application ID:** 10187785
- **Project number:** 3R01DC004450-22S1
- **Recipient organization:** OREGON HEALTH & SCIENCE UNIVERSITY
- **Principal Investigator:** LAURENCE O TRUSSELL
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $63,812
- **Award type:** 3
- **Project period:** 1999-09-01 → 2023-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10187785

## Citation

> US National Institutes of Health, RePORTER application 10187785, Synaptic mechanisms in the auditory system (3R01DC004450-22S1). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10187785. Licensed CC0.

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