Learned helplessness: Validity and reliability of depressive-like states in mice

doi:10.1016/j.brainresprot.2005.09.002

Brain Research Protocols

Volume 16, Issues 1–3, December 2005, Pages 70-78

https://doi.org/10.1016/j.brainresprot.2005.09.002 Get rights and content

Abstract

The learned helplessness paradigm is a depression model in which animals are exposed to unpredictable and uncontrollable stress, e.g. electroshocks, and subsequently develop coping deficits for aversive but escapable situations (J.B. Overmier, M.E. Seligman, Effects of inescapable shock upon subsequent escape and avoidance responding, J. Comp. Physiol. Psychol. 63 (1967) 28–33 [15]). It represents a model with good similarity to the symptoms of depression, construct, and predictive validity in rats. Despite an increased need to investigate emotional, in particular depression-like behaviors in transgenic mice, so far only a few studies have been published using the learned helplessness paradigm. One reason may be the fact that—in contrast to rats (B. Vollmayr, F.A. Henn, Learned helplessness in the rat: improvements in validity and reliability, Brain Res. Brain Res. Protoc. 8 (2001) 1–7)—there is no generally accepted learned helplessness protocol available for mice. This prompted us to develop a reliable helplessness procedure in C57BL/6N mice, to exclude possible artifacts, and to establish a protocol, which yields a consistent fraction of helpless mice following the shock exposure. Furthermore, we validated this protocol pharmacologically using the tricyclic antidepressant imipramine. Here, we present a mouse model with good face and predictive validity that can be used for transgenic, behavioral, and pharmacological studies.

Section snippets

Type of research

(1)
The protocol described here allows murine studies of molecular, neurochemical, stress-physiological, and behavioral consequences of the learned helplessness paradigm, a behavioral model of depression.
(2)
A detailed characterization of this model, defining a time course of coping deficits (helplessness) and employing clearly structured definitions of helpless behavior, also evaluated by pharmacological treatment, supplies good validity and reliability of this model.
(3)
As a result, this protocol can be

Time required

The course of the learned helplessness paradigm starts with an inescapable shock procedure on two consecutive days, each of these shock sessions lasting approximately 52 min. Learned helplessness is assessed 24 h after the second shock procedure and lasts up to 24 min, depending on the animals' performance in the shuttle box. More then 80% of helpless animals remain helpless for at least 1 week (Fig. 1).

Special equipment

The shock procedure was applied in a transparent plexiglas shock chamber (18 × 18 × 30 cm³), equipped with a stainless steel grid floor (diameter of each grid: 0.5 cm, spacing: 0.6 cm) (Coulborn precision regulated animal shocker, Coulborn Instruments, Düsseldorf, Germany).

The two-way avoidance test was conducted in a two-compartment shuttle box (Coulborn Instruments, Düsseldorf, Germany), equipped with infrared-light beams at the bottom of each of the two compartments to monitor spontaneous

Animals

10-week-old male C57BL/6N mice were purchased from Charles River, Sulzfeld, Germany, and acclimatized to single housing in macrolon cages (type II) at constant conditions with a 12 h dark–light cycle and an average room temperature of 22 °C for 2 weeks prior to the experiments, with food and water ad libitum. All experiments were approved by German animal welfare authorities (Regierungspräsidium Karlsruhe).

Inescapable shock procedure

(1)
Mice were exposed to inescapable shocks during their active (dark) phase. Animals had to

Definition of helplessness

Cluster analysis (Fig. 2) is a group of exploratory data analysis tools, which aim at sorting different objects into groups in a way that the degree of association between two objects is maximal if they belong to the same group and minimal otherwise. Thus, cluster analysis can be used to discover structures in data without providing an explanation or interpretation. Among the different clustering algorithms available, we used the k-means procedure, because it allows the a priori specification

Setup of the protocol

In order to establish a valid and reliable mouse model of depression as it has been described in rats [25], we designed a learned helplessness procedure, in which two series of unpredictable and uncontrollable footshocks applied over 2 days under dark conditions evoke helpless performance in a shuttle box, while controllable shock “immunizes” against helplessness. This is in line with most rodent depression models that use stress as a tool to induce depression-like symptoms.

Time course

Supporting the face

Quick procedure

(a)
Expose the mice to 360 scrambled footshocks (intensity: 0.150 mA) on two consecutive days.
(b)
24 h later, perform a two-way avoidance paradigm (30 shuttle escape trials) in a shuttle box.
(c)
Analyze the data by considering “failures” and “escape latency” as the most relevant parameters for the identification of helpless animals.

Alternative protocols

Training procedures reported previously, based on the paradigm by Shanks and Anisman (1988) and Caldarone et al. (2000) may represent alternative protocols [2], [21]. In these protocols, learned helplessness is induced by administering 120 inescapable 4 s footshocks (0.30 mA) with a random interval (range 3–50 s) over a 1 h session. Training is given in two sessions that are spaced approximately 24 h apart. Mice are placed on either side of the shock chamber, so that the shock is administered

Essential literature references

[2], [4], [5], [6], [10], [12], [13], [16], [20], [22], [25], [27]

Acknowledgments

This work was supported by grants from the Deutsche Forschungsgemeinschaft to P.G. (GA427/4-2, SFB636/B3). S.C. had a scholarship from the GK 791, University of Heidelberg.

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Discriminant analysis

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View full text

Learned helplessness: Validity and reliability of depressive-like states in mice

Abstract

Section snippets

Type of research

Time required

Special equipment

Animals

Inescapable shock procedure

Definition of helplessness

Setup of the protocol

Time course

Quick procedure

Alternative protocols

Essential literature references

Acknowledgments

Pharmacol. Biochem. Behav.

Behav. Brain Res.

Pharmacol. Biochem. Behav.

Biol. Psychiatry

Prog. Neuro-Psychopharmacol. Biol. Psychiatry

Biol. Psychiatry

Life Sci.

Pharmacol. Biochem. Behav.

Brain Res. Brain Res. Protoc.

Comparison of two-phase treatment with imipramine or fluvoxamine, both followed by lithium addition, in inpatients with major depressive disorder

Am. J. Psychiatry

In search of a depressed mouse: utility of models for studying depression-related behavior in genetically modified mice

Mol. Psychiatry

Discriminant analysis

Sage University Paper Series on Quantitative Applications in the Social Sciences, 07-038