Analysis of Electrocardiograms and Behavior in Mice from Pregnancy to Lactation Period

Summary

A simultaneous recording of autonomic activity and detailed maternal behavior of mother mice from pregnancy to lactation was achieved using a telemetry system. This method helps to understand the dynamics of the physiological and behavioral characteristics in mothers from pregnancy to weaning.

Abstract

Changes in the mother-offspring relationship are presumably accompanied by dynamic changes in the autonomic nervous system. Although temporal measurements of autonomic activity have been performed in human mothers and infants, the analysis of long-term changes remains unexplored. Mouse mothers can form social bonds with their pups and have a short period of pregnancy and lactation, which makes them useful for the examination of physiological changes from pregnancy to pup-rearing. Therefore, a telemetry system was used for several weeks to measure the changes in the autonomic nervous system and the behavior of mouse mothers. The current results showed that an electrocardiogram (ECG) could be stably recorded regardless of the movements of mothers and parturition. ECG analysis showed that the heart rate gradually decreased from pregnancy to lactation, and sympathetic activity sharply increased as the pups developed. Furthermore, the simultaneous recording of behavior and ECG in the home cage enabled us to understand the behavior-dependent influences on the ECG, thereby revealing the characteristics of autonomic nervous activity during each behavior. Thus, the present experimental method helps to understand how the physiological characteristics of mothers change from pregnancy through pup rearing, supporting the healthy development of pups.

Introduction

The mother-offspring relationship is unique among the relationships established by various animal species owing to its great impact on the future of the offspring¹. In humans, the development and internal/external behaviors of children are influenced by parenting style as well as the extent of abuse and neglect^2,3. Similarly, in rodents, the quality of maternal behavior has a significant impact on pup development and behavior^4,5,6. Therefore, detailed tracking and examination of the nurturing b....

Protocol

All procedures were approved by the Ethics Committee of Azabu University (#210319-30). C57B/6J mice at gestational day (GD) 14 weighing over 22 g were used for the present study. The animals were obtained from a commercial source (see Table of Materials). The reagents and equipment needed for the study are listed in the Table of Materials.

1. Experimental preparation

1. Turn on the panel heater and cover it with aluminum foil. Wipe al.......

Discussion

In this method, wherein the telemeter was implanted into pregnant mice, the ECG could be continuously tracked in the same mouse from pregnancy to lactation. The mouse exhibited ethograms that included movement, indicating wakefulness during all analysis periods (23:32-23:42) from GD 17 to PD 21. Additionally, the present results showed that the heart rate gradually decreased from pregnancy to lactation. This decrease is considered to be due to the normalization of the heart rate, as several studies have shown that heart .......

Materials

Name	Company	Catalog Number	Comments
24-h repeating timer	Panasonic	WH3311BP
5-0 Nylon suture	Natsume Seisakusho Co	-23s-N2
Anesthesia box	Natsume Seisakusho Co	KN-1010	W110×D110×H110mm
Anesthesia mask	Natsume Seisakusho Co	KN-1019-1
Anesthesic machine	Natsume Seisakusho Co	KN-1071-E
C57BL6/J mice	Clea Japan, Inc		Pregnancy mouse at 14 day
Clip light	Yazawa corporation	CLX60X02WH
Configurator System	Adinstuments	TR190
drive recorder	Transcend	TS-DP250A-32G
Food holder	Clea Japan, Inc	CL-2802
Isoflurane	FujiFilM	099-06571
LabChart Pro V8	Adinstuments	MLU260/8
LabChart8	Adinstuments	MLS060/8
Mouse Biopotential Telemeter	Adinstuments	MT10B
Needle 18 G 1 1/2	Terumo	NN-1838R
Panel heater	SANKO	4976285145407
PowerLab 4/26	Adinstuments	PL2604
Recordable computer	Mouse computer	mouse K7-H
red light bulb	ELPA	LDG1R-G-GWP254
Rubber mask	Natsume Seisakusho Co	KN-1019-M
SD card (256GB)	Transcend	TS256GUSD350V	It can record approximately 24 h
Suture needle 13 mm	Natsume Seisakusho Co	C-24-540-NO.0
Suture needle 7 mm	Natsume Seisakusho Co	C-24-540-NO.0000
tBase	Adinstuments	MT110