A Chronic Immobilization Stress Protocol for Inducing Depression-Like Behavior in Mice

Summary

This article provides a simplified and standardized protocol for induction of depressive-like behavior in chronically immobilized mice by using a restrainer. In addition, behavior and physiological techniques to verify induction of depression are explained.

Abstract

Depression is not yet fully understood, but various causative factors have been reported. Recently, the prevalence of depression has increased. However, therapeutic treatments for depression or research on depression is scarce. Thus, in the present paper, we propose a mouse model of depression induced by movement restriction. Chronic mild stress (CMS) is a well-known technique to induce depressive-like behavior. However, it necessitates a complex procedure consisting of a combination of various mild stresses. In contrast, chronic immobilization stress (CIS) is a readily accessible chronic stress model, modified from a restraint model that induces depressive behavior by restricting movement using a restrainer for a certain period. To evaluate the depressive-like behaviors, the sucrose preference test (SPT), the tail suspension test (TST), and the ELISA assay to measure stress marker corticosterone levels are combined in the present experiment. The described protocols illustrate the induction of CIS and evaluation of the changes in behavior and physiological factors for the validation of depression.

Introduction

Major depressive disorder (MDD) is the leading cause of mental disability worldwide, with an incidence that is increasing faster than anticipated. In 2001, the World Health Organization predicted that MDD would be the second most common disease in the world by 2020. However, it was already the second most common in 2013¹. In addition, current antidepressants have many limitations, including delayed effectivity, drug resistance, relapse, and various side effects^2,3. Researchers must therefore develop more effective antidepressants. However, the ambiguous pathophysiology of MDD presents a....

Protocol

All experimental protocols and animal care were conducted according to the guidelines of the University Animal Care Committee for Animal Research of Gyeongsang National University (GLA-100917-M0093).

1. Materials

1. Mice
   1. Use males of C57BL/6 strain background weighing 22–24 g at postnatal week 7. Habituate in the breeding room for 1 week before the experiments.
      NOTE: All mice were purchased from a laboratory animal company.
   2. House mice individually in a temperature-controlled vivarium (22–24 °C) under a 12-hour light/dark cycle (lights on at 6:00 A.M.), with normal laboratory chow and ....

Results

In the representative experiment, all data were acquired from 6 - 8 mice per group. Representative materials and the method to insert the mouse voluntarily into the restrainer are shown in Figure 1.

To perform the behavioral test and blood sampling after CIS induction, mice were subjected to the experimental procedure as summarized in Figure 2A. As shown in Figure 2 and Figure 3

Discussion

The complexity of the brain and heterogeneity of MDD make it challenging to create animal models that completely reproduce the condition. Many researchers have overcome this difficulty using an endophenotype-based approach³², in which anhedonia (lack of interest in rewarding stimuli) and despair are considered evolutionarily conserved and quantifiable behaviors in animal models, which are also seen in patients with depression³³. In the present paper, we have presented a met.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
1 ml disposable syringes	Sungshim Medical	P000CFDO
Balance	A&D Company	FX-2000i
Ball nozzle	Jeung Do B&P	JD-C-88
CCTV camera	KOCOM	KCB-381
Corticosterone ELISA kits	Cayman Chemical
Digital lux meter	TES	TES-1330A
Ethovision XT 7.1	Noldus Information Technology
Isoflurane	HANA PHARM CO., LTD.		Ifran solution
Mice	Koatech		C57BL/6 strain
Restrainer	Dae-jong Instrument Industry	DJ-428
Saccharose (sucrose)	DAEJUNG	7501-4400
Small animal isoflurane anaesthetic system	Summit
Acrylic bar			The apparatus was made in the lab for TST test
Tail suspension box			The apparatus was made in the lab
Timer	Electronics Tomorrow	TL-2530
Water bottle	Jeung Do B&P	JD-C-79