Chronic Transcranial Electrical Stimulation and Intracortical Recording in Rats

Summary

This detailed protocol describes transcranial stimulation electrode placement on the temporal bone in order to investigate the short- and long-term effects of transcranial electrical stimulation in freely moving rats.

Abstract

Transcranial electrical stimulation (TES) is a powerful and relatively simple approach to diffusely influence brain activity either randomly or in a closed-loop event-triggered manner. Although many studies are focusing on the possible benefits and side-effects of TES in healthy and pathologic brains, there are still many fundamental open questions regarding the mechanism of action of the stimulation. Therefore, there is a clear need for a robust and reproducible method to test the acute and the chronic effects of TES in rodents. TES can be combined with regular behavioral, electrophysiological, and imaging techniques to investigate neuronal networks in vivo. The implantation of transcranial stimulation electrodes does not impose extra constraints on the experimental design while it offers a versatile, flexible tool to manipulate brain activity. Here we provide a detailed, step-by-step protocol to fabricate and implant transcranial stimulation electrodes to influence brain activity in a temporally constrained manner for months.

Introduction

Transcranial electrical stimulation (TES) is a valuable methodological approach to influence brain activity in a temporally constrained manner. Depending on the size and placement of the stimulation electrodes, TES can affect large brain volumes and entrain neuronal populations diffusely^1,2,3. Transcranial direct current stimulation is already medically approved for the treatment of major depressive disorder^4,5, and many studies focus on showing the cognitive effects of transcranial stimulation in humans

Protocol

All methods described here are in accordance with the directives of the European Communities Council (86/609 ECC) and have been approved by the Ethical Committee for Animal Research at the Albert Szent-Györgyi Medical and Pharmaceutical Center of the University of Szeged (XIV/218/2016).

1. Fabrication of the Stimulation Electrodes

1. To make one stimulation electrode, cut six 10 cm long pieces of miniature hook-up wires, remove 2 cm of the cladding on one end, and 1 cm on the other end.
2. Twist two cables together and solder them at the shorter peeled side.
3. Acquire a strip of three tape packaging of any integ....

Results

The implantation of chronic stimulation electrodes (Figure 1B) can be combined with additional implantation of recording electrodes (Figure 1C-D). Such settings are suitable to form on-demand recording and stimulation systems to interfere with specific brain activities. Here we present representative results of a closed-loop epilepsy detection and intervention system, applied on Long-Evans rats expressing spontan.......

Discussion

The most critical step of this protocol is the gluing of the electrode package on the bone surface. In case of improper sealing, a gap is formed between the electrodes and the bone, and secondary scar tissue can grow into this gap, which lessens the quality of stimulation. The bone surface must be completely dry during the steps of sticking on the package, and in the case of experiencing instability of the electrodes, it must be removed and replaced with a new package to gain the best results.

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Cyanoacrylate liquid	Henkel	Loctite 401
Cyanoacrylate gel	Henkel	Loctite 454
Wire for stimulation electrodes	Phoenix Wire Inc.	36744MHW - PTFE Microminiature Hook-Up Wire
Board spacer	E-tec Interconnect	SP1-020-S378/01-55
Connector	E-tec Interconnect	P2510I-02
Tape packaging for stimulation electrodes	Nexperia	74HC1G00GW	Tape packaging of any integrated circuit with SOT-353 case can be used
Grip Cement Industrial Grade	Caulk Dentsply	675571 (powder) 675572 (solvent)
Electroconductive gel	Rextra	ECG Gel
Recording electrode wire	California Fine Wire Co.	.002 (50 micron) Tungsten 99.95% (CFW Material #: 100-211), HMl-Natural, cut to 3.0 inch pieces, Round, Cut length piece wire
Ultrafine scissors	Hammacher Instrumente	Stainless HSB 544-09
Stainless steel tube	Vita Needle Company	29 RW, 304SS Tubing, T.I.G. Welded and Plug
High speed rotary saw	Dremel	Model # 395
Rotary saw holder	Dremel	Model # 220
Rotary saw cut-off wheel	Dremel	Model # 409
Ocular sticks	Lohmann-Rauscher	Pro-ophta Ocular Sticks
Wet disinfectant	Egis	Betadine
Dry disinfectant	Wagner Pharma	Reseptyl-urea
Drilling machine	NSK-Nakanishi United Kingdom	Vmax35RV Pack
Anchoring screws	Antrin Miniature Specialties, Inc.	000-120x1/16 SL BIND MS SS