Elsevier

Physiology & Behavior

Volume 118, 13 June 2013, Pages 227-239
Physiology & Behavior

Review
Factors influencing behavior in the forced swim test

https://doi.org/10.1016/j.physbeh.2013.05.012Get rights and content

Highlights

  • The forced swim test (FST) is a rodent behavioral test for antidepressant efficacy.

  • Variability in the FST results complicates the comparison across studies.

  • The available literature was analyzed for factors influencing the FST behavior.

  • The role of biological factors, preconditioning and experimental design is described.

Abstract

The forced swim test (FST) is a behavioral test in rodents which was developed in 1978 by Porsolt and colleagues as a model for predicting the clinical efficacy of antidepressant drugs. A modified version of the FST added the classification of active behaviors into swimming and climbing, in order to facilitate the differentiation between serotonergic and noradrenergic classes of antidepressant drugs. The FST is now widely used in basic research and the pharmaceutical screening of potential antidepressant treatments. It is also one of the most commonly used tests to assess depressive-like behavior in animal models. Despite the simplicity and sensitivity of the FST procedure, important differences even in baseline immobility rates have been reported between different groups, which complicate the comparison of results across studies.

In spite of several methodological papers and reviews published on the FST, the need still exists for clarification of factors which can influence the procedure. While most recent reviews have focused on antidepressant effects observed with the FST, this one considers the methodological aspects of the procedure, aiming to summarize issues beyond antidepressant action in the FST. The previously published literature is analyzed for factors which are known to influence animal behavior in the FST. These include biological factors, such as strain, age, body weight, gender and individual differences between animals; influence of preconditioning before the FST: handling, social isolation or enriched environment, food manipulations, various kinds of stress, endocrine manipulations and surgery; schedule and routes of treatment, dosage and type of the drugs as well as experimental design and laboratory environmental effects. Consideration of these factors in planning experiments may result in more consistent FST results.

Introduction

Major depressive disorder is a global medical problem due to its high prevalence and incomplete responsiveness to treatment [1]. Screening of novel antidepressants is an important practice in modern research due to the limited efficacy and large number of side effects of existing treatments [2]. The forced swim test (FST), also known as the ‘behavioral despair’ test, was developed in 1978 by Porsolt et al. [3] as a rodent model for predicting the clinical efficacy of antidepressant drugs.

The basic FST involves two sessions with animals placed in a cylinder containing 25 °C water, from which they cannot escape. The first session is a 15-min pretest that is followed 24 h later by a 5-min test session. The pretest is a stressor which is thought to induce a state of behavioral despair [4] or passive stress coping strategy [5], since the animals become more immobile as the test session progresses. The typical posture of immobility is characterized by floating in the water with only movements necessary to keep the nose above the surface. The immobility time and also the latency to the initial immobility period [6] are the primary dependent measures. A wide range of antidepressant drugs injected between the pretest and test periods decrease the duration of immobility in the test, i.e., makes the rats more active [7].

In 1996, Detke and coauthors added evaluation of active behavior during the FST — climbing: vertical movements against walls; swimming: horizontal movements across the water surface; and diving. This modified version facilitates differentiation between the major classes of antidepressant drugs in rats [8]. Treatment with norepinephrine-targeting antidepressants selectively increases climbing in the FST, while drugs influencing serotonin neurotransmission enhance swimming behavior. Adding measurement of the latency to immobility to the standard procedure increases the sensitivity of the FST in both mice and rats [6], [9].

The FST is also used for assessment of depressive-like behavior in animal models of psychiatric disorders [10], [11], [12]. The behavioral and biochemical characteristics of animals in a state of learned helplessness produced by a period of inescapable swimming during the FST have led some investigators to believe this condition itself provides a useful animal model of depression [13], [14]. Forced swim provokes neurochemical and endocrine alterations [15], [16] and is used as a stressor by itself [17], [18].

Despite the simplicity and sensitivity of the FST procedure, large differences even in baseline immobility rates have been reported between different working groups, which complicate the comparison of results across studies. To illustrate this, some examples of differences in immobility scored in control animals of the two most commonly used strains of rats, Sprague–Dawley and Wistar, are presented in Table 1.

In this review, we have analyzed the published literature included in the PubMed MEDLINE database for factors that may influence rodent behavior in the FST and attempt to describe those variables that should be considered in studies employing the FST. First, factors which are known to influence FST results were chosen (e.g. physical environmental factors such as light and noise; biological factors such as age, sex, and strain; and manipulations before test, such as housing and handling). As the FST was developed for the rat, and active behaviors estimated mostly for the rat, keywords for this search included “factor of interest + forced swim test + rat”. Sometimes, due to a low number of search results, (less than 10), keywords were changed to “factor of interest + forced swim test”, and results from other species, mostly mice, were included. If the search yielded more than 1000 results (as in the case of antidepressant treatment), only reviews were considered.

Section snippets

Strain of animals

Behavioral strategies in the FST can vary significantly with animal strain [53], [54], [55]. Even obtaining Wistar or Sprague–Dawley rats from different suppliers may yield different findings [4]. A significant decrease of struggling between first and second sessions of the FST was observed in spontaneously hypertensive (SHR) and Wistar Kyoto (WKY) but not in Fisher 344 or Lewis (LEW) rats [55]. Strain differences also exist in antidepressant efficacy [28], [56], [57].

Certain specific rat

Handling

Short-term handling daily for 5 days prior to the FST did not affect immobility time in rats, but long-term handling (2 months daily before the FST) increased immobility time in the study [84] (Table 2).

Housing

Exposing laboratory animals to physical or social stimulation greater than they would receive under standard housing conditions either had no effect on immobility [36], [85] or had an antidepressant-like effect (Table 2).

Rats housed in an enriched environment exhibited less immobility [3] and more

Test equipment and settings

Tank dimensions play a significant role in determining behavior in the FST. In Porsolt's original version of the test, the tank was 40 cm in height and 18 cm in diameter; it was designed to have depth of 15 cm water, shallow enough for the rat to feel the bottom with its hind paws and tail [3]; animals developed a floating posture quickly and this resulted in more immobility during the second test session. The modified version of the FST involved increasing water depth to 30 cm, so the rat was

Conclusions

The FST, in its classical or modified version, provides a unique opportunity to assess antidepressant efficacy in a rapid, low-cost, and reliable manner. Its strong predictive and discriminative validity serves for reliable assessment of neurological mechanisms of antidepressant action. A large and growing number of studies also use the FST to assess depressive-like behavior in animal models of mood disorders.

To summarize, there are several suggestions which may help to improve quality of the

Acknowledgments

This research is supported by funds from the Utah Science Technology and Research (USTAR) initiative and the VISN19 MIRECC to Dr. Perry Renshaw.

References (225)

  • S. Morley-Fletcher et al.

    Prenatal stress in rats predicts immobility behavior in the forced swim test. Effects of a chronic treatment with tianeptine

    Brain Res

    (2003)
  • H. Abe et al.

    Prenatal psychological stress causes higher emotionality, depression-like behavior, and elevated activity in the hypothalamo–pituitary–adrenal axis

    Neurosci Res

    (2007)
  • J.W. Jahng et al.

    Chronic food restriction in young rats results in depression- and anxiety-like behaviors with decreased expression of serotonin reuptake transporter

    Brain Res

    (2007)
  • D.M. Kokare et al.

    Involvement of alpha-MSH in the social isolation induced anxiety- and depression-like behaviors in rat

    Neuropharmacology

    (2010)
  • N. Calvo et al.

    Differential effects of social defeat in rats with high and low locomotor response to novelty

    Neuroscience

    (2011)
  • C. Lopez-Rubalcava et al.

    Strain differences in the behavioral effects of antidepressant drugs in the rat forced swimming test

    Neuropsychopharmacology

    (2000)
  • P.M. Pitychoutis et al.

    Individual differences in novelty-seeking predict differential responses to chronic antidepressant treatment through sex- and phenotype-dependent neurochemical signatures

    Behav Brain Res

    (2011)
  • P.F. Renshaw et al.

    Lovastatin potentiates the antidepressant efficacy of fluoxetine in rats

    Pharmacol Biochem Behav

    (2009)
  • P.J. Allen et al.

    Sex-specific antidepressant effects of dietary creatine with and without sub-acute fluoxetine in rats

    Pharmacol Biochem Behav

    (2012)
  • J. Simpson et al.

    Effect of early life housing manipulation on baseline and drug-induced behavioural responses on neurochemistry in the male rat

    Prog Neuropsychopharmacol Biol Psychiatry

    (2012)
  • J.C. Brenes et al.

    Differential effect of environment enrichment and social isolation on depressive-like behavior, spontaneous activity and serotonin and norepinephrine concentration in prefrontal cortex and ventral striatum

    Pharmacol Biochem Behav

    (2008)
  • D.A. White et al.

    Locomotor response to novelty as a predictor of reactivity to aversive stimuli in the rat

    Brain Res

    (2007)
  • C. Estanislau et al.

    Individual differences in the elevated plus-maze and the forced swim test

    Behav Processes

    (2011)
  • J. Veena et al.

    Exposure to enriched environment restores the survival and differentiation of new born cells in the hippocampus and ameliorates depressive symptoms in chronically stressed rats

    Neurosci Lett

    (2009)
  • P. Vieyra-Reyes et al.

    Antidepressant-like effects of nicotine and transcranial magnetic stimulation in the olfactory bulbectomy rat model of depression

    Brain Res Bull

    (2008)
  • C. Lino-de-Oliveira et al.

    Structure of the rat behaviour in the forced swimming test

    Behav Brain Res

    (2005)
  • F.S. Hall et al.

    The effects of social isolation on the forced swim test in Fawn hooded and Wistar rats

    J Neurosci Methods

    (1998)
  • J. Harro et al.

    Chronic variable stress and partial 5-HT denervation by parachloroamphetamine treatment in the rat: effects on behavior and monoamine neurochemistry

    Brain Res

    (2001)
  • R. Haidkind et al.

    Effects of partial locus coeruleus denervation and chronic mild stress on behaviour and monoamine neurochemistry in the rat

    Eur Neuropsychopharmacol

    (2003)
  • G. Drossopoulou et al.

    Sex differences in behavioral, neurochemical and neuroendocrine effects induced by the forced swim test in rats

    Neuroscience

    (2004)
  • L. Martinez-Mota et al.

    Testosterone-dependent antidepressant-like effect of noradrenergic but not of serotonergic drugs

    Pharmacol Biochem Behav

    (2004)
  • C. Dalla et al.

    Sex differences in the effects of two stress paradigms on dopaminergic neurotransmission

    Physiol Behav

    (2008)
  • T.J. Mezadri et al.

    Repeated rat-forced swim test: reducing the number of animals to evaluate gradual effects of antidepressants

    J Neurosci Methods

    (2011)
  • D. Consoli et al.

    Stressors affect the response of male and female rats to clomipramine in a model of behavioral despair (forced swim test)

    Eur J Pharmacol

    (2005)
  • A. Armario et al.

    Comparison of the behavioural and endocrine response to forced swimming stress in five inbred strains of rats

    Psychoneuroendocrinology

    (1995)
  • J. Marti et al.

    Forced swimming behavior is not related to the corticosterone levels achieved in the test: a study with four inbred rat strains

    Physiol Behav

    (1996)
  • S. Tejani-Butt et al.

    Strain-dependent modification of behavior following antidepressant treatment

    Prog Neuropsychopharmacol Biol Psychiatry

    (2003)
  • W.P. Pare

    Stress ulcer susceptibility and depression in Wistar Kyoto (WKY) rats

    Physiol Behav

    (1989)
  • O. Malkesman et al.

    Two different putative genetic animal models of childhood depression — a review

    Prog Neurobiol

    (2009)
  • C.W. Fischer et al.

    Isolation-induced behavioural changes in a genetic animal model of depression

    Behav Brain Res

    (2012)
  • E.L. Abel

    Response to alarm substance in different rat strains

    Physiol Behav

    (1992)
  • F.Z. Shaw et al.

    Depression- and anxiety-like behaviors of a rat model with absence epileptic discharges

    Neuroscience

    (2009)
  • I.P. Butkevich et al.

    Heterogeneity of the infant stage of rat development: inflammatory pain response, depression-related behavior, and effects of prenatal stress

    Brain Res

    (2009)
  • E.L. Abel

    Ontogeny of immobility and response to alarm substance in the forced swim test

    Physiol Behav

    (1993)
  • L. Martinez-Mota et al.

    Sex and age differences in the impact of the forced swimming test on the levels of steroid hormones

    Physiol Behav

    (2011)
  • G. Yates et al.

    Social isolation effects on the “behavioral despair” forced swimming test: effect of age and duration of testing

    Physiol Behav

    (1991)
  • C.M. Contreras et al.

    Desipramine restricts estral cycle oscillations in swimming

    Prog Neuropsychopharmacol Biol Psychiatry

    (1998)
  • N. Kokras et al.

    Behavioral sexual dimorphism in models of anxiety and depression due to changes in HPA axis activity

    Neuropharmacology

    (2012)
  • C.H. Bourke et al.

    Behavioral effects of chronic adolescent stress are sustained and sexually dimorphic

    Horm Behav

    (2011)
  • P.A. Scott et al.

    Susceptibility and resistance of rats to stress-induced decreases in swim-test activity: a selective breeding study

    Brain Res

    (1996)
  • Cited by (301)

    • Biomarkers of fatigue in oncology: A systematic review

      2024, Critical Reviews in Oncology/Hematology
    View all citing articles on Scopus
    View full text