Simple Surgical Induction of Conductive Hearing Loss with Verification Using Otoscope Visualization and Behavioral Clap Startle Response in Rat

Summary

Here, we present a protocol to establish a replicable conductive hearing loss induction via surgical tympanic membrane puncture and verification by otoscope visualization and behavioral assessment by clap startle.

Abstract

Conductive hearing loss (CHL) is a prevalent hearing impairment in humans. The goal of the protocol is to describe a simple surgical procedure for inducing CHL in rodents. The protocol demonstrates CHL by tympanic membrane puncture. Verification of CHL surgery was by otoscope examination and behavioral assessment by clap startle response, both replicable and reliable, and are simple methods to demonstrate hearing loss has occurred. The simple CHL procedure is advantageous due to its reproducibility and flexibility to different pursuits in hearing loss research. The limitations of inducing CHL by a surgical approach are associated with the learning curve to perform the surgical procedure and confidence in audiological examination. Inducing a hearing impairment by CHL allows one to readily study the neural manifestations and behavioral outcomes of hearing loss.

Introduction

The prevalence of the hearing loss in children and adults is approximately 19.5%¹ and 15.2%² respectively. However, approximately 39.3% of all newborns with an abnormal hearing screening do not receive remedial treatment as reported by the Centers for Disease Control³. Hearing loss is a widely studied condition, and the rodent is a robust model to study normal hearing and hearing related disorders^{4,5,6,7,8,9....}

Protocol

The present study and procedures were approved by the animal research ethics committees of the City University of Hong Kong, the University of Hong Kong, and the Department of Health of the Hong Kong Special Administrative Region.

1. Animals

1. Use Sprague-Dawley (SD) rats of two months (N = 90, 200-250 g).
   NOTE: Rodents were provided by the accredited Laboratory Animal Unit of the University of Hong Kong.
2. Maintain the rats under a constant 25 °C temperature and 60-70% humidity at the Laboratory Animal Research Unit.
3. House rodents in 12/12-h light/dark cycles with access to food and drinking water, <....

Results

The simple CHL procedure was performed on 90 rats and out of this group 2 had significant bleeding and 2 did not have hearing loss the next day as assessed by behavioral clap startle. These four rats were discarded. Rats should be discarded as described by the reasons in the discussion due to complications. Inducing TM puncture and/or malleus displacement/removal (Figure 2B) elicits CHL, which results in behavioral manifestations (i.e. CHL - no response to lo.......

Discussion

We describe a simple surgical induction of CHL with verification using otoscope visualization and behavioral clap startle response in rat. Here we demonstrate the method on rat and previously this method has been applied to gerbils and mice. The method can easily be adopted to other rodents. Induction of CHL allows the study of a subtle form of hearing loss which manifests in auditory cortical alterations and psychophysical behavioral findings^4,5,

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Latex, polyvinyl or nitrile gloves	AMMEX		Use unpowdered gloves 8-mil
Micro spring scissors (see Fig. 1b)	RWD Life Science	S11035-08	8.0 cm total length, with 3.5mm cutting edge, or similar micro forceps. Standard tweezers with spring action will suffice
Otoscope mini 3000	HEINE	D-008.70.120M	Standard LED otoscope will suffice
Rat or mouse	JAX labs		Any small rodent
Small rodent cage	Tecniplast	1284L	Need two cages to separate CHL rodent from hearing rodent. If rodents are in direct contact with one-another, they will startle each other. Cage dimensions 365 x 207 x 140 mm, floor area: 530 cm2/82.15 in2