Using a Bipolar Electrode to Create a Temporal Lobe Epilepsy Mouse Model by Electrical Kindling of the Amygdala

Summary

The amygdala plays a key role in temporal lobe epilepsy, which originates in and propagates from this structure. This article provides a detailed description of the fabrication of deep brain electrodes with both recording and stimulating functions. It introduces a model of medial temporal lobe epilepsy originating from the amygdala.

Abstract

The amygdala is one of the most common origins of seizures, and the amygdala mouse model is essential for the illustration of epilepsy. However, few studies have described the experimental protocol in detail. This paper illustrates the whole process of amygdala electrical kindling epilepsy model making, with the introduction of a method of bipolar electrode fabrication. This electrode can both stimulate and record, reducing brain injury caused by implanting separate electrodes for stimulation and recording. For long-term electroencephalogram (EEG) recording purposes, slip rings were used to eliminate the record interruption caused by cable tangles and falling off.

After periodic stimulation (60 Hz, 1 s every 15 min) of the basolateral amygdala (AP: 1.67 mm, L: 2.7 mm, V: 4.9 mm) for 19.83 ± 5.742 times, full kindling was observed in six mice (defined as induction of three continuous grade V episodes classified by Racine's scale). An intracranial EEG was recorded throughout the entire kindling process, and an epileptic discharge in the amygdala lasting 20-70 s was observed after kindling. Therefore, this is a robust protocol for modeling epilepsy originating from the amygdala, and the method is suitable for revealing the role of the amygdala in temporal lobe epilepsy. This research contributes to future studies on the mechanisms of mesial temporal lobe epilepsy and novel antiepileptogenic drugs.

Introduction

Temporal lobe epilepsy (TLE) is the most prevalent type of epilepsy and has a high risk of conversion into drug-resistant epilepsy. Surgery, such as selective amygdalohippocampectomy, is an effective treatment for TLE, and the epileptogenesis and ictogenesis of the disease are still under investigation^1,2. Pathogenesis of TLE has been shown to occur not only in the hippocampus but also extensively in the amygdala^3,4. For example, both amygdala sclerosis and amygdala enlargement have been frequently reported as the origins of TLE seizures

Protocol

This experiment was approved by the Experimental Animal Ethics Committee of Xuanwu Hospital, Capital Medical University. All mice were kept in the animal laboratory of Xuanwu Hospital, Capital Medical University. This protocol is divided into four parts. The first two parts introduce the method of building the electrode and the electric circuit using a slip ring to connect the electrodes and the EEG recording/stimulation equipment. The third part describes the operation method of electrode implantation, and the fourth part presents the EEG recording and stimulation parameters used for the amygdala epilepsy model.

1. Fabrication of ele....

Results

The electrode and circuit enable the EEG to be recorded and function as a stimulation (Figure 1); this setup avoids the complexity of implanting recording and stimulating electrodes separately and minimizes damage to the brain tissue. The application of slip rings allows electrode connection with all types of devices.

We performed electrode implantation surgery on six healthy adult male C57BL/6 mice, and electrical stimulation was performed 2 weeks after surgery. .......

Discussion

Epilepsy is a group of diseases with multiple manifestations and diverse causes¹⁸; it should be noted that no single model can be used for all types of epilepsy, and researchers must select an appropriate model for their specific study. The present study introduces one of the most accessible methods of electrode fabrication. Various parts of this method can be adjusted to adapt to different experimental conditions.

This method utilizes electrodes with both stimulating a.......

Materials

Name	Company	Catalog Number	Comments
Alexa Fluor 488-conjugated Donkey anti-Rabbit IgG	invitrogen	A-21206
c-Fos antibody		ab222699
Cranial drill	SANS	SA302
dental cement	NISSIN
EEG recording and stimulation equipment	Neuracle Technology (Changzhou) Co., Ltd	NSHHFS-210803
lead-free tin wire	BAKON
Pin header/Female header	XIANMISI		spacing of 1.27 mm
Silver wire	A-M systems	786000
Slip ring	Senring Electronics Co.,Ltd	SNM008-04
Tungsten wire	A-M systems	796000
ultrafine multi-stand wire	Shenzhen Chengxing wire and cable	UL10064-FEP
welding equipment	BAKON	BK881