Facial Nerve Surgery in the Rat Model to Study Axonal Inhibition and Regeneration

Summary

This protocol describes a reproducible approach to facial nerve surgery in the rat model, including descriptions of various inducible patterns of injury.

Abstract

This protocol describes consistent and reproducible methods to study axonal regeneration and inhibition in a rat facial nerve injury model. The facial nerve can be manipulated along its entire length, from its intracranial segment to its extratemporal course. There are three primary types of nerve injury used for the experimental study of regenerative properties: nerve crush, transection, and nerve gap. The range of possible interventions is vast, including surgical manipulation of the nerve, delivery of neuroactive reagents or cells, and either central or end-organ manipulations. Advantages of this model for studying nerve regeneration include simplicity, reproducibility, interspecies consistency, reliable survival rates of the rat, and an increased anatomic size relative to murine models. Its limitations involve a more limited genetic manipulation versus the mouse model and the superlative regenerative capability of the rat, such that the facial nerve scientist must carefully assess time points for recovery and whether to translate results to higher animals and human studies. The rat model for facial nerve injury allows for functional, electrophysiological, and histomorphometric parameters for the interpretation and comparison of nerve regeneration. It thereby boasts tremendous potential toward furthering the understanding and treatment of the devastating consequences of facial nerve injury in human patients.

Introduction

Cranial nerve injury in the head and neck region can be secondary to congenital, infectious, idiopathic, iatrogenic, traumatic, neurologic, oncologic, or systemic etiologies¹. Cranial nerve VII, or the facial nerve, is commonly affected. The incidence of facial nerve dysfunction can be significant, as it affects 20 to 30 per 100,000 people each year². The main motor branches of the facial nerve are the temporal, zygomatic, buccal, marginal mandibular, and cervical branches; depending on the branch involved, the consequences can include oral incompetence or drooling, corneal dryness, visual field obstruction secondary to ....

Protocol

All interventions were performed in strict accordance with the National Institutes of Health (NIH) guidelines. The experimental protocol was approved by the University of Michigan's Institutional Animal Care & Use Committee (IACUC) prior to implementation. Ten-week-old adult female Sprague-Dawley rats were utilized.

1. Prior to the operative day

1. Ensure an appropriate stock of sterilized surgical instruments, analgesic medications, anesthetic medication, and oxygen prior to .......

Discussion

The rat facial nerve injury model has emerged as the most versatile system for the evaluation of neurotrophic factors due to its surgical accessibility, branching pattern, and physiological significance^{27,29,33,34,35,36}. The combination of video demonstration and application of transgenic animal data opens new possibilities f.......

Materials

Name	Company	Catalog Number	Comments
1.8% isoflurane	VetOne	13985-030-40
11-0 nylon microsutures	AROSuture	TK-117038
4-0 monocryl suture	VWR	75982-084
Buprenorphine SR	ZooPharm	MIF 900-006
Carprofen	Sigma-Aldrich	MFCD00079028
Chlorhexidine	VWR	IC19135805
Jeweler forceps	VWR	21909-458
Micro Weitlaner retractor	VWR	82030-146
Micro-scissors	VWR	100492-348
Mini tenotomy scissors	VWR	89023-522
Number 15 scalpel blade	VWR	102097-834
Operating microscope	Leica
Petrolatum eye gel	Pharmaderm	B002LUWBEK
Sterile water	VWR	89125-834
Tissue adhesive	Vetbond, 3M	NC9259532
Water conductor pad	Aqua Relief System	ARS2000B