Preparation of Peripheral Nerve Stimulation Electrodes for Chronic Implantation in Rats

Summary

Existing approaches for constructing chronically implantable peripheral nerve cuff electrodes for use in small rodents often require specialized equipment and/or highly trained personnel. In this protocol we demonstrate a simple, low-cost approach for fabricating chronically implantable cuff electrodes, and demonstrate their effectiveness for vagus nerve stimulation (VNS) in rats.

Abstract

Peripheral nerve cuff electrodes have long been used in the neurosciences and related fields for stimulation of, for example, vagus or sciatic nerves. Several recent studies have demonstrated the effectiveness of chronic VNS in enhancing central nervous system plasticity to improve motor rehabilitation, extinction learning, and sensory discrimination. Construction of chronically implantable devices for use in such studies is challenging due to rats’ small size, and typical protocols require extensive training of personnel and time-consuming microfabrication methods. Alternatively, commercially available implantable cuff electrodes can be purchased at a significantly higher cost. In this protocol, we present a simple, low-cost method for construction of small, chronically implantable peripheral nerve cuff electrodes for use in rats. We validate the short and long-term reliability of our cuff electrodes by demonstrating that VNS in ketamine/xylazine anesthetized rats produces decreases in breathing rate consistent with activation of the Hering-Breuer reflex, both at the time of implantation and up to 10 weeks after device implantation. We further demonstrate the suitability of the cuff electrodes for use in chronic stimulation studies by pairing VNS with skilled lever press performance to induce motor cortical map plasticity.

Introduction

Recently, the demand for chronically implantable cuff electrodes for stimulation of peripheral nerves has grown, as studies increasingly demonstrate the preclinical usefulness of this technique for the treatment of numerous inflammatory diseases^1,2,3 and neurological disorders^{4,5,6,7,8,9,10,11,}

Protocol

All procedures described in this protocol are carried out in accordance with the NIH Guide for the Care and Use of Laboratory Animals and were approved by the Institutional Animal Care and Use Committee of The University of Texas at Dallas.

1. Stimulating cuff electrode fabrication

1. Prepare the cuff tubing.
   1. Using a razor blade, cut a piece of polymer tubing 2.5 mm in length. Insert forceps tips or a paper clip through the tubing and use the blade to make a slit lengthwis.......

Discussion

Here we describe a simple, low-cost approach for assembly of chronically implantable stimulating cuff electrodes for use in rodents, facilitating preclinical investigations of this emerging therapy. This simplified method requires no specialized training or equipment, and uses a small number of tools and supplies that are easily accessible to most research labs, reducing both the monetary and labor costs of device manufacture compared to other approaches^16,26

Materials

Name	Company	Catalog Number	Comments
Biocompatible polyurethane-based polymer tubing, 0.080" OD x 0.040" ID	Braintree Scientific	MRE080 36 FT
Dissecting microscope	AM Scopes	#SM-6T-FRL
Fine Serrated Scissors, straight, 22mm cutting edge	Fine Science Tools	#14058-09	for cutting Pt/Ir wire and suture thread
Forceps, #5 Dumont forceps, straight, 11 cm, 0.1 x 0.06 mm tip	Fine Science Tools	#11626-11
Forceps, ceramic tipped forceps, 0.3 mm x 30 mm tips	Electron Microscopy Sciences	#78127-71
Gold Pins, PCB Press Fit Socket	Mill-Max	#1001-0-15-15-30-27-04-0	or similar small pins for connecting cuff leads to headcap
Isobutane lighter	BIC	#LCP21-AST	for de-insulating Pt/Ir wire
Micro strip connector with latch, 4-pin	Omnetics	A24002-004 / PS1-04-SS-LT
Pipette tip, 10 uL	VWR	89079-464
Platinum-Iridium (90/10%) Wire, 0.001" (diameter) x 9 strands, PTFE insulated	Sigmund Cohn	10IR9/49T
Razor Blade, Single Edge, Surgical Carbon Steel No.9	VWR	#55411-050	for cutting MicroRenathane tubing
Sewing needle, ca. 4.0 cm length x 0.7 mm diameter (size 6-7)	Singer	00276	Smaller needle for threading Pt/Ir wire
Sewing needle, ca. 4.5 cm length x 0.8 mm diameter (size 2-3)	Singer	00276	Larger needle for pinning cuff during assembly and for threading suture
Small foam board	Juvo+/Amazon	B07C9637SJ	for fabrication platform; our dimensions are ca. 2.5" x 3.5" x 1" (L x W x H)
Solder, multicore lead-free, 0.38mm diameter	Loctite/Multicore	#796037
Soldering station	Weller	WES51	or similar soldering iron compatible with long conical tips (this part has been discontinued)
Soldering tip, long conical, 0.01" / 0.4 mm	Weller	1UNF8
Suture, nonabsorbable braided silk ,size 6/0	Fine Science tools	#18020-60
UV (405 nm) spot light	Henkel/Loctite	#2182207
UV Light Cure Adhesive 25 ml	Henkel/Loctite	AA 3106	or similar biocompatible UV cure adhesive
Wire wrapping wire, 30 AWG	Digikey	K396-ND