Postoperative Recovery and Stability of Chronic Intracranial Multielectrode Electroencephalography Recording in Rats

Summary

This protocol outlines a standardized framework for post-surgical evaluation after chronic multi-electrode EEG implantation in rats, including sequential monitoring of signal quality, behavioral recovery, and neuroinflammatory markers to determine appropriate initiation of stable long-term recordings.

Abstract

Intracranial multi-electrode implantation enables simultaneous acquisition of neural signals across brain regions but introduces post-surgical perturbations that can affect data quality and experimental timing. This protocol describes a standardized workflow for chronic multi-site intracranial EEG electrode implantation and structured post-implantation assessment in Sprague–Dawley rats. Tungsten wire electrodes are stereotactically implanted at three predefined intracranial sites (anterior cingulate cortex, hippocampus CA1, and entorhinal cortex) using a surgical strategy designed to minimize tissue disruption.

Following implantation, the protocol specifies longitudinal evaluation across five domains: electrode localization accuracy, local field potential integrity, pain-related behavior, feeding behavior, and neuroinflammatory markers. Electrophysiological and behavioral assessments are conducted at predefined postoperative time points (baseline and postoperative days 1, 4, 7, 10, and 13) to support consistent monitoring of early post-surgical effects (n = 3). Histological analyses are used to characterize local tissue responses at the end of the study (n = 3 per time point).

Operational criteria and assessment intervals are provided to guide decisions regarding experimental readiness and initiation of long-term recordings. This protocol provides a structured approach to post-implantation monitoring and informs the appropriate timing of downstream neurophysiological experiments.

Introduction

Intracranial electroencephalography (EEG) enables high-resolution measurement of neural activity by recording signals directly from brain tissue^1,2, providing advantages in spatial specificity and signal fidelity over scalp EEG approaches³. Multiple-region intracranial recordings offer insights into network-level interactions, which are widely used to investigate neural dynamics underlying cognition and disease and are commonly implemented in rodent models for mechanistic and longitudinal studies^4,5.

....

Protocol

All animal procedures were performed in accordance with institutional guidelines and approved by the Institutional Animal Care and Use Committee of Capital Medical University (Approval ID: AEEI-2024-391).

1. Animal preparation

1. Obtain 6-week-old male SD rats (body weight 220–230 g). House the animals in a specific pathogen-free environment (24 ± 2 °C, 50 ± 10% humidity, 12 h light/dark cycle). Provide food and water ad libitum. Acclimate the rats for 7 days prior to surgery.
2. Following electrode implantation, house rats individually under the same environmental conditions to....

Results

All 21 SD rats tolerated intracranial electrode implantation and completed the study protocol. Longitudinal measures (EEG, body weight, feeding behavior, and pain scores) were collected from the same animals across time points (n = 3), while neuroinflammatory assessments were terminal measures at each time point (n = 3 rats per day: baseline, 1, 4, 7, 10, 13). Data were assessed for normality using Shapiro-Wilk tests. Normally distributed data are expressed as mean ± SEM and compared using one-way or repeated-measures AN.......

Discussion

Chronic intracranial electrode implantation for EEG monitoring in rodents remains a cornerstone technique for investigating neural dynamics at high temporal resolution. Establishing an appropriate postoperative monitoring and recovery window is critical for ensuring both signal reliability and animal welfare. This study provides a structured framework for evaluating electrophysiological stability, behavioral outcomes, and inflammatory responses following multi-electrode implantation in SD rats, offering practical guidanc.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Active isofluorane scavening system	RDW	R510-31-6
Animals	Charles River
BCA assay kit	Solarbio	PC0020
ChemiDoc Imaging System	Bio-Rad	17001401
Dental resin	Vertex	XG473P03
ECL detection reagent	Solarbio	PE0010
Erythromycin eye ointment	Renhe	1.00E+11
Goat anti-rabbit secondary antibody	Proteintech	SA00001-2
GraphPad Prism 9.0	GraphPad Software		statistical analysis software
Headstage amplifier	BIOPAC Systems Inc	EEG100C
Heating pad	YuYan technology	S-100
ImageJ	National Institutes of Health		image analysis software
IL-6 polyclonal antibody	Proteintech	21865-1-AP
Iodophore	Cleanboom	430-DFXDY100
Isoflurane	RWD	R510–31
Neuro-recording device with NeuroExplorer (v 5.012)	Plexon	OPX-A1600-128-16C	electrophysiological data analysis software
PVDF membrane	Cytiva	RPN303F
SDS-PAGE System	Bio-Rad	1658004
Stereotaxic apparatus	ZhongShi science technology	ZS-PDC
TNF-αpolyclonal antibody	Proteintech	17590-1-AP
Transfer Apparatus	Bio-Rad	1703937
Tungsten wire	A-M Systems	785500
Video recording system	Basler	acA1920
β-actin monoclonal antibody	Proteintech	2D4H5