Surgical Labyrinthectomy of the Rat to Study the Vestibular System

Summary

This protocol describes the surgical labyrinthectomy of a rat, which is a useful method for studying the vestibular system.

Abstract

To study the vestibular system or the vestibular compensation process, a number of methods have been developed to cause vestibular damage, including surgical or chemical labyrinthectomy and vestibular neurectomy. Surgical labyrinthectomy is a relatively simple, reliable, and rapid method. Here, we describe the surgical technique for rat labyrinthectomy. A postauricular incision is made under general anesthesia to expose the external auditory canal and the tympanic membrane, after which the tympanic membrane and the ossicles are removed without the stapes. The stapes artery, which is located between the stapes and the oval window, is a vulnerable structure and must be preserved to obtain a clear surgical field. A hole to fenestrate the vestibule is made with a 2.1-mm drill bur superior to the stapes. Then, 100% ethanol is injected through this hole and aspirated several times. Meticulous dissection under a microscope and careful bleeding control are essential to obtain reliable results. Symptoms of vestibular loss, such as nystagmus, head tilting, and a rolling motion, are seen immediately after surgery. The rotarod or rotation chair test can be used to objectively and quantitatively evaluate the vestibular function.

Introduction

The vestibular organ is essential for balance and eye control. A normal vestibular function depends upon symmetrical afferent signals from the vestibular organs in the two inner ears. Vestibular hypofunction or loss induces dizziness, nystagmus, and postural imbalance. After acute damage, the vestibular function recovers spontaneously within several days, a process known as vestibular compensation^1,2. The vestibular compensation of static deficits is a process of recovery related to the imbalance of spontaneous resting activity between the ipsilateral and contralateral vestibular nuclei. The vestibular compens....

Protocol

This study was performed in accordance with the Institutional Animal Care and Use Committee of Seoul National University Hospital (14-0148-C1A1), which is accredited by the Association for the Assessment and Accreditation of Laboratory Animal Care International.

NOTE: The experiments were performed on Sprague-Dawley (SD) male rats of 7 - 8 weeks old (200/250 g). Each animal was acclimatized to the laboratory conditions for 1 week prior to the start of the experiment. The animals were housed in a temperature- and humidity-controlled room with a constant 12-h:12-h light:dark cycle with free access to food and water.

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Results

The success of the surgery was validated by behavioral tests. All animals exhibited the typical behavior of a unilateral loss of vestibular function. Spontaneous barrel-rolling was evident immediately after surgery, being evoked by an air puff over the head or a light touch to the body in the early recovery phase (Video 1). 3 d after surgery, the animals moved around leaning toward the lesioned side with occasional falls to the left side. Spontaneous nystagmus was observe.......

Discussion

This technique is a useful method for creating sudden, permanent, and complete vestibular function loss. This could be used to study vestibular pathologies, such as vestibular neuritis, an acoustic tumor, and Meniere's disease. Many studies have used this technique to study the neuronal plasticity of vestibular nuclei or the related central process^5,17,18,19.

The.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
ASPIRATOR KB-012	KOH BONG & CO., LTD.	KB-012	Medical aspirator
Blade: #15	Fine Science Tools	#10015-00	Blades for #7 Scalpel Handles, #15
Carbon Steel Burrs	Fine Science Tools	#19007-05	shaft diameter: 2.3 mm, length: 44 mm, package of 10 burrs
Carl Zeiss Surgical GmbH	Carl Zeiss	#6627100863	Surgical microscope
Dumont #3c	Fine Science Tools	#11231-20	Standard tip 0.17 x 0.10 mm, 11 cm
Dumont #5SF	Fine Science Tools	#11252-00
Dumont #7B	Fine Science Tools	#11270-20	Serrated 0.17 x 0.10 mm, 11 cm
Extra Fine Bonn: straight	Fine Science Tools	#14084-08	Iris scissors, best suited for microdissection under high magnification
Fine Iris Scissors: straight	Fine Science Tools	#14094-11	Made from martensitic stainless steel, combined with molybdenum and vanadium
Finger Loop Ear Punch	Fine Science Tools	#24212-01	1 mm. Provides stability and control for researchers using the numbering system
Hartman	Fine Science Tools	#13002-10	Tip width: 1 cm, serrated, 10 cm
Short Scalpel Handle #7 Solid	Fine Science Tools	#10003-12	#7 short, 12 cm
Small Vessel Cauterizer	Fine Science Tools	#18000-03	Replacement tip, straight knife, keeps bleeding to a minimum and therefore provides a surgical field clear of clamps and hemostats
Strong 207S	SAESHIN	207S	Powerful torque at low speed, available with speed or on/off foot controller
Suction Tubes	JEUNGDO B&P CO., LTD.	H-1927-8	Frazier, 18 cm
VICRYL	ETHICON	W9570T	Synthetic absorbable sterile surgical suture
Weitlaner-Locktite	Fine Science Tools	#17012-13	Maximum spread: 4.5 cm, 2 x 3 blunt teeth, 11 cm
Zoletil	Virbac, France		Tiletamine-zolazepam
Rompun	Bayer		Xylazine
Rimadyl	Pfizer		Carprofen
Septra	Pfizer		Trimethoprim-sulfonamide