Abstract
Objectives:
Optogenetics is a powerful new tool to use for the auditory system and involves the introduction of a light-sensitive protein into neurons. This exciting approach may help to increase spatial resolution of auditory implants that are limited due to electrical current spread and to improve outcomes. Herein, we describe: (1) generation of a novel transgenic mouse expressing channelrhodopsin-2 (ChR2+) in spiral ganglion cells (SGC), (2) auditory responses to optical stimulation of the cochlea in our ChR2+ transgenic mouse.
Methods:
A left cochleostomy was performed and the right inferior colliculus (IC) was exposed via craniotomy in adult ChR2+ mice. Optically evoked auditory brainstem responses (oABRs) and IC multi-unit recordings were conducted in response to optical stimulation via a blue-light laser fiber (473nm wavelength) placed into the cochleostomy. The expression of ChR2 in cochlea was histologically identified under confocal microscope.
Results:
ChR2 expression was observed in the soma, the peripheral and central axons of almost all SGCs in 1 to 7- month-old ChR2+ mice. A single 1-ms blue light pulse can evoke oABRs with peak magnitudes up to 10uV and latencies short as 2 ms. Evoked multi-unit activity (~180 spikes/second) in the IC was substantially synchronized (0.9 synchronization index) to a 28-Hz light pulse train applied in cochlea.
Conclusions:
We generated and characterized a novel ChR2 transgenic mouse line that is sensitive to light-based stimulation in the peripheral auditory system. Our study may demonstrate the feasibility of using optogenetic technology as the basis for new neuronal stimulation paradigm for cochlear implants.
Get full access to this article
View all access options for this article.